https://kbwiki.ercoftac.org/w/api.php?action=feedcontributions&user=Mike&feedformat=atom KBwiki - User contributions [en] 2024-03-29T11:25:56Z User contributions MediaWiki 1.39.2 https://kbwiki.ercoftac.org/w/index.php?title=Description_AC1-05&diff=45224 Description AC1-05 2024-03-04T10:37:41Z <p>Mike: /* Introduction */</p> <hr /> <div>{{AC|front=AC 1-05|description=Description_AC1-05|testdata=Test Data_AC1-05|cfdsimulations=CFD Simulations_AC1-05|evaluation=Evaluation_AC1-05|qualityreview=Quality Review_AC1-05|bestpractice=Best Practice Advice_AC1-05|relatedUFRs=Related UFRs_AC1-05}}<br /> <br /> ='''Ahmed body'''=<br /> <br /> '''Application Challenge 1-05''' © copyright ERCOFTAC 2004<br /> <br /> <br /> <br /> =='''Introduction'''==<br /> <br /> A basic ground vehicle type of bluff body is investigated. The body consists of three parts : a fore-body, a mid section and a rear end.<br /> <br /> Two experiments are available:<br /> <br /> The first one (Exp1) was performed at DLR-Göttingen in a wind tunnel at Reynolds number 4.29 million (60 m/s), based on the model length. The model is mounted on a ground plate, in order to reproduce the ground effect. The angle of the rear end slope is adjustable, between 0 and 40° with a 5° step. More details are available for angles of 5°, 12.5° and 30°. Pressure is measured by about 210 pressure probes on the fore-body, 83 in the mid section and 450 on rear ends. Friction lines <br /> visualizations are also available. Moreover, detailed wake surveys are performed with 10 hole probes and drag measurements are provided.<br /> <br /> <br /> <br /> The second, more recent experiment (Exp2) was provided by Erlangen LSTM within the MOVA “Models for Vehicle Aerodynamics” European project (TU Delft, Univ. of Manchester (UMIST), LSTM, Electricité de France, AVL List, PSA Peugeot-Citroën). The same model is used as in the previous study, but the Reynolds number is reduced to 2.78 million (40m/s), and the study is focused on slant angles close to the drag crisis, 25° and 35°. Two-component hot wire measurements were performed in the boundary layer above the slant part and LDA measurements in 13 different planes. Mean values and turbulence statistics (second and third moments) are provided. Pressure measurements were performed on the rear part of the model (435 pressure probes). Oil/soot friction lines visualizations are also provided.<br /> <br /> The Ahmed body was one of the test cases of the 9th and 10th ERCOFTAC-IAHR Workshop on Refined Turbulence Modeling held in Darmstad, Germany (2001) and Poitiers, France (2002) respectively. These workshops were organized under the auspices of the Special Interest Group 15 on Turbulence Modeling of ERCOFTAC. The proceedings of the 10th ERCOFTAC-IAHR Workshop can be found at:<br /> <br /> [https://hal.science/hal-03037095 https://hal.science/hal-03037095]<br /> <br /> and this test case at:<br /> <br /> [{{filepath:Ahmed.florian.menter.pdf}} Test case 9.4].<br /> <br /> CFD results were obtained by 15 different teams, ranging from simple RANS models (standard k-epsilon model with wall functions) to more elaborate RANS models and even LES.<br /> <br /> After the ERCOFTAC workshops in the early 2000’s, CFD simulations were mainly carried out with LES and hybrid RANS-LES methods. An update on these simulations was added in 2024 to this document by F.R. Menter including LES results for the 25° slant angle case from Menter et al (2024) - Reference see Abstract.<br /> <br /> =='''Relevance to Industrial Sector'''==<br /> <br /> The basic shape of the so-called « Ahmed body » contains important features of real road vehicles : a main body, followed by a fully separated region. Prediction of separated flows is one of the more difficult task of CFD. The parametric variation of the angle of the rear part allows the study of various configuration relevant to real car characteristics, from massively separated, “simple” wakes, to very complex, 3D wake structures. The reproduction of this complex, 3D wake is very challenging for CFD, as well as the transition from one behaviour to another. The data base contains also drag results that are essential to predict for practical purposes, and are closely related to the structure of the wake.<br /> <br /> The second set of experiments provides very detailed results, including turbulent quantities that are useful for a detailed analysis of turbulence models.<br /> <br /> <br /> =='''Design or Assessment Parameters'''==<br /> <br /> The first [[DOAP]] is the drag coefficient, and in particular its variations with the slant angle.<br /> <br /> A second [[DOAP]] is the topology of the flow, which is crucial for the correct reproduction of the drag coefficient. Comparisons between computations and experiments in the provided planes and in the boundary layer will be useful, as well as friction lines visualizations on the slant part and the vertical base.<br /> <br /> <br /> =='''Flow Domain Geometry'''==<br /> <br /> <br /> {|align=&quot;center&quot;<br /> |[[Image:Image22.gif]]<br /> |-<br /> |''Figure 1:'' Geometry of the Ahmed body <br /> |}<br /> <br /> <br /> <br /> The model is described on Figure 1. The geometry of the fore-body is available in<br /> &lt;span class=&quot;plainlinks&quot;&gt;[{{filepath:Ahmed_Front_Geo.dat}} Ahmed_Front_Geo.dat]&lt;/span&gt;.<br /> <br /> X, Y and Z are the streamwise, spanwise and ground-normal directions, respectively. The origin of the axes is the point at the intersection between the vertical base (X=0), the symmetry plane (Y=0) and the ground plate (Z=0).<br /> <br /> Overall length: 1.044 m. Width 0.389 m, Height 0.288 m.<br /> <br /> The forebody is 0.182 m long, the center of the curvature being placed 100 mm from the front and upper/lower/lateral surfaces. The central (constant section area) is 0.640 m long.<br /> <br /> All rear ends have the same slant part length Ls= 222mm. The edges are sharp.<br /> <br /> The model is placed in a 3/4-open test section (only the floor is present). No indication on the homogeneity of the flow is given.<br /> <br /> Special attention should be given on the presence of a ground plate between the tunnel floor and the body. This plate is used for preventing wind tunnel boundary layer parasitic effects on the model. The model lies 50 mm above it and is placed on stilts of 30 mm diameter.<br /> <br /> =='''Flow Physics and Fluid Dynamics Data'''==<br /> <br /> The flow has no special characteristics. Air at ambiant conditions is used. The model is supposed to be smooth.<br /> <br /> © copyright ERCOFTAC 2004<br /> <br /> ----<br /> <br /> <br /> ''Contributors: Remi Manceau; Jean-Paul Bonnet - Université de Poitiers. &amp;mdash; Update (2024) F.R.Menter, ANSYS Germany '', <br /> <br /> <br /> {{AC|front=AC 1-05|description=Description_AC1-05|testdata=Test Data_AC1-05|cfdsimulations=CFD Simulations_AC1-05|evaluation=Evaluation_AC1-05|qualityreview=Quality Review_AC1-05|bestpractice=Best Practice Advice_AC1-05|relatedUFRs=Related UFRs_AC1-05}}</div> Mike https://kbwiki.ercoftac.org/w/index.php?title=Evaluation_AC1-05&diff=45223 Evaluation AC1-05 2024-03-04T10:36:25Z <p>Mike: /* Comparison of Test data and CFD */</p> <hr /> <div>{{AC|front=AC 1-05|description=Description_AC1-05|testdata=Test Data_AC1-05|cfdsimulations=CFD Simulations_AC1-05|evaluation=Evaluation_AC1-05|qualityreview=Quality Review_AC1-05|bestpractice=Best Practice Advice_AC1-05|relatedUFRs=Related UFRs_AC1-05}}<br /> <br /> ='''Ahmed body'''=<br /> <br /> '''Application Challenge 1-05''' © copyright ERCOFTAC 2004<br /> <br /> <br /> <br /> =='''Comparison of Test data and CFD'''==<br /> <br /> Experiments provide very detailed data that offer a particularly difficult challenge to CFD. They showed that the drag crisis experienced by the body around 25°-30° is related to a dramatic change of the structure of the wake. The low-drag configuration (35°) consists in a massively separated wake, which is quasi-2D, while the high-drag configuration (25°) consists in a very complex, 3D wake structure, with a reattachment of the flow on the slant part and a strong interaction of the bubble with intense corner vortices, which are very energy-consuming.<br /> <br /> EXP1 shows that fixing a splitter plate in the wake of the body, in the symmetry plane, forces the flow to turn back to the low drag configuration (massively separated wake). The mechanism underlying these phenomena is not clear, but it could be due to the fact that the splitter plate counteracts a flapping of the wake in the span-wise direction. Therefore, there are some evidences that large-scale unsteadiness of the wake could play a crucial role in the wake structure transition. It could also explain high levels of turbulent stresses above the slant part that are very difficult to predict with steady-state RANS calculations.<br /> <br /> It appears from all the CFD results that the wake structure of the low drag configurations (35°) is correctly reproduced by all the turbulence models tested. The correct trend of the drag coefficient with the slant angle is correctly reproduced (CFD1), but the correct level is not found. In general, since the wake structure is correct, the pressure levels on the slant part are realistic, but the exact pressure repartition on the slant part and the vertical base are hardly reproduced.<br /> <br /> <br /> Concerning the high-drag configuration (25°), the great majority of the CFD computations were not able to reproduce the complex, 3D structure of the wake: a massively separated wake is obtained, which shows that the wake structure transition is missed. The number of computation and the variety of numerical schemes and meshes give many indications that the main issue is not numerical, but linked to the physical modeling: turbulence model and steady-state strategy. It appears that only two types of modeling are able to reproduce the structure of the wake: LES (CFD9) and low-Reynolds number Reynolds stress model (CFD13). It should indicate that the large-scale unsteadiness of the wake must be resolved (the potential of URANS has not been investigated extensively yet) or, alternatively, the absence of large-scale unsteadiness resolution must be compensated by a very refined turbulence modeling (Reynolds stress transport equations and integration down to the wall). However, these partial conclusions are only based on one LES and one low-Re RSM computation. Additional studies are necessary to confirm these favorable conclusions.<br /> <br /> <br /> The paper of Florian Menter extracted from the Proceedings of the 10th ERCOFTAC IAHR Workshop (https://hal.science/hal-03037095) with permission, gives a further comparison of experimental and CFD results, including various figures. This paper can be obtained by clicking [{{filepath:Ahmed.florian.menter.pdf}} here].<br /> <br /> ==='''Update added in 2024 by F.R. Menter'''===<br /> <br /> Since the ERCOFTAC workshops, simulations have progressed with an increased focus on Scale-Resolving Simulations. The simulations fall in two categories: Hybrid RANS-LES model and pure LES model simulations. Hybrid RANS-LES methods seem well suited for the Ahmed 25° car. They avoid the high cost of LES near the wall of the attached boundary layers. The ability of such models to predict the complex flow topology for the 25° case depends however on the ability of the underlying RANS model to predict separation from the slant onset. For a discussion of hybrid methods with application to this current test case see e.g. [https://hal.science/hal-02874819/document Guilminesau et al. (2020)], [https://www.sciencedirect.com/science/article/pii/S0167610520302117 Ekman et al. (2020)].<br /> <br /> The application of LES to the 25° case proved surprisingly difficult. Up to the publication by [https://link.springer.com/article/10.1007/s10494-023-00472-9 Menter et al (2024)] no LES with acceptable accuracy for the exp. Reynolds number has been achieved. For a review of LES studies see [https://link.springer.com/article/10.1007/s10494-023-00472-9 Menter et al (2024)]. Of special interest is that simulations at artificially reduced Reynolds number were able to predict the correct flow topology with separation and reattachment on the slant, even on coarse grids. However, at the exp. Reynolds number, the simulations showed a similar behavior to RANS models. In one set of simulations, the flow stayed attached (like with k- type models) and in another set, the flow stalled (like with SST type models). The authors in [https://link.springer.com/article/10.1007/s10494-023-00472-9 Menter et al (2024)] confirmed this observation, even for much finer meshes than used previously (e.g. a 560 million block-structured hexahedral mesh resulted in fully attached flow). Only after turning to Octree meshes, which allow a three-dimensional refinement towards the wall, could a sufficient resolution of the boundary layer be achieved to allow a reliable prediction of separation and reattachment on the slant. The following pictures are taken from [https://link.springer.com/article/10.1007/s10494-023-00472-9 Menter et al (2024)].<br /> <br /> {|align=&quot;center&quot;<br /> |[[Image:Ac1_05_figure_2.png|600px|center|]]<br /> |-<br /> |''Figure 2:'' Zoom of Octree meshes O1 and O2 near the roof-slant intersection. <br /> |}<br /> <br /> {|align=&quot;center&quot;<br /> |[[Image:Ac1_05_figure_3a.png|600px|center|]]<br /> |-<br /> |[[Image:Ac1_05_figure_3b.png|600px|center|]]<br /> |-<br /> |''Figure 3:'' Flow structure on roof-center plane for WALE O1(top) and WALE O2 (bottom) meshes showing contours of vorticity. <br /> |}<br /> <br /> {|align=&quot;center&quot;<br /> |[[Image:Ac1_05_figure_4.png|600px|center|]]<br /> |-<br /> |''Figure 4:'' Wall shear stress on the roof-center plane for WALE- O2 and WALE- O1 in comparison with SBES/RANS solution. <br /> |}<br /> <br /> <br /> Fig. 2 shows two Octree meshes near the roof-slant onset of the Ahmed car. The coarser mesh has 230 million and the refined mesh has 320 million cells. Both grids are formally of sufficient near-wall resolution for a wall-resolved LES (with ∆x^+=∆z^+≈35,∆y^+=1 in streamwise, spanwise and wall-normal direction respectively). However, the 320 million cell mesh (O1) has an overall finer mesh in the central part of the boundary layer. This results in a resolution of finer turbulence structures in the roof boundary layer as seen in Fig.3. The improved resolution brings the LES closer to the wall shear stress distribution (Cf) of the SST/SBES model which can serve as a reliable reference for the zero-pressure gradient flow in that region (Fig.4).<br /> <br /> <br /> {|align=&quot;center&quot;<br /> |[[Image:Ac1_05_figure_5.png|600px|center|]]<br /> |-<br /> |''Figure 5:'' Velocity profiles in center plane for WRLES on O1 and O2 grids, compared to experimental data. <br /> |}<br /> <br /> {|align=&quot;center&quot;<br /> |[[Image:Ac1_05_figure_6.png|600px|center|]]<br /> |-<br /> |''Figure 6:'' Stress profiles for streamwise coordinate in center plane for WRLES on O1 and O2 grids, compared to experimental data. <br /> |}<br /> <br /> Both meshes produce highly accurate representations of the separation bubble on the slant as seen from the velocity profiles in Fig. 5. Included in the figure is also a simulation on the O1 mesh where the WALE model was deactivated in the entire domain, which resulted in an even slightly better agreement with the experimental data. Fig. 6 shows the corresponding profiles for the streamwise stress component, which are again in good agreement with the experimental data, in contrast to RANS models which strongly underpredicted the stress level. While there are acceptable velocity profile results available for hybrid models e.g. [https://hal.science/hal-02874819/document Guilmineau et al. (2020)], also none of these simulations captures the correct stress-level, especially just downstream of the slant onset. This points to a high consistency of the depicted LES simulations. <br /> <br /> <br /> {|align=&quot;center&quot;<br /> |[[Image:Ac1_05_figure_7a.png|400px]][[Image:Ac1_05_figure_7b.png|400px]]<br /> |-<br /> |''Figure 7:'' : Flow topology on slant of Ahmed car. Left: experimental oil flow (from Ahmed et al 1984). Right: Octree O1 – no model simulation. <br /> |}<br /> <br /> Figure 7 shows the flow topology for the O1 (no model) simulation compared to the experimental oil flow. As expected from the close agreement in the velocity profiles, the agreement in the flow pattern is also very close. <br /> <br /> <br /> {|align=&quot;center&quot;<br /> |[[Image:Ac1_05_figure_8.png|600px|center|]]<br /> |-<br /> |''Figure 8:'' Q-criterion plots for Octree O1 no model solution. Large picture has &lt;math&gt;Q=5 \cdot 10^6s^{-2}&lt;/math&gt; and smaller picture has &lt;math&gt;Q=1 \cdot 10^8s^{-2}&lt;/math&gt;. <br /> |}<br /> <br /> Finally, Figure 8 shows the resolved turbulence structures using the Q-criterion with a zoom to the slant onset region for the O1 mesh. As seen, this mesh allows for a very fine resolution of the turbulence which is necessary to accurately capture flow reattachment.<br /> <br /> =='''References'''==<br /> Ekman , P., Wieser, D., Virdung, T., Karlsson, M., Assessment of hybrid RANS-LES methods for accurate aerodynamic simulations. J. of wind Engg. And Industrial Aerodynamics, 206, (2020), 104301.<br /> <br /> Guilmineau E., Deng G.B., Leroyer A., Queutey P. Visonneau M., Wackers J., Assessment of hybrid RANS-LES formulations for flow simulation around the Ahmed body. Comput. Fluids 176, 302-319 (2018) <br /> <br /> Menter,F.R., Hüppe A., Flad D., Garburak, A. V., Matyushenko A.A., Stabnikov A.S., Large eddy simulations for the Ahmed car at 25° slant angle at different Teynolds numbers. Flow, Turbulence and Combustion, 112, 321-343, (2024).<br /> <br /> © copyright ERCOFTAC 2004<br /> <br /> <br /> ----<br /> <br /> ''Contributors: Remi Manceau; Jean-Paul Bonnet - Université de Poitiers. &amp;mdash; Update (2024) F.R.Menter, ANSYS Germany '', <br /> <br /> <br /> {{AC|front=AC 1-05|description=Description_AC1-05|testdata=Test Data_AC1-05|cfdsimulations=CFD Simulations_AC1-05|evaluation=Evaluation_AC1-05|qualityreview=Quality Review_AC1-05|bestpractice=Best Practice Advice_AC1-05|relatedUFRs=Related UFRs_AC1-05}}</div> Mike https://kbwiki.ercoftac.org/w/index.php?title=CFD_Simulations_AC1-05&diff=45222 CFD Simulations AC1-05 2024-03-04T10:35:54Z <p>Mike: /* Overview of CFD Simulations */</p> <hr /> <div>{{AC|front=AC 1-05|description=Description_AC1-05|testdata=Test Data_AC1-05|cfdsimulations=CFD Simulations_AC1-05|evaluation=Evaluation_AC1-05|qualityreview=Quality Review_AC1-05|bestpractice=Best Practice Advice_AC1-05|relatedUFRs=Related UFRs_AC1-05}}<br /> <br /> ='''Ahmed body'''=<br /> <br /> '''Application Challenge 1-05''' © copyright ERCOFTAC 2004<br /> <br /> <br /> <br /> =='''Overview of CFD Simulations'''==<br /> <br /> CFD simulations have developed rapidly during the writing of the present document, during the MOVA consortium and in the frame of the 9th and 10th ERCOFTAC-IAHR Workshop on Refined Turbulence Modeling organized in Darmstad, Germany and Poitiers, France, in 2001 and 2002, respectively. These workshops were organized under the auspices of the Special Interest Group 15 on Turbulence Modeling of ERCOFTAC. The proceedings of the 10th ERCOFTAC-IAHR Workshop can be found at:<br /> <br /> [https://hal.science/hal-03037095 https://hal.science/hal-03037095]<br /> <br /> For the 10th ERCOFTAC-IAHR Workshop, several recommendations were made to the groups participating in the CFD calculations. Among them the recommendation to extend the computational domain up to 5 times the car length downstream of the body, and the possibility to omit the stilts.<br /> <br /> Many of the CFD results are considered by the authors themselves as preliminary computations and were therefore not inserted into the knowledge base.<br /> <br /> The geometry is simple enough to be satisfactorily represented.<br /> <br /> =='''Simulation Case CFD1'''==<br /> <br /> ==='''Solution strategy CFD1'''===<br /> <br /> RANS modelling.<br /> <br /> Commercial FLUENT 4.2 code, based on unstructured finite volume discretization.<br /> <br /> Reynolds number: 4.29x106 (see EXP1). Steady state computation.<br /> <br /> The slant angle is varied from 0 to 50 degrees.<br /> <br /> <br /> ==='''Computational Domain CFD1'''===<br /> <br /> Symmetry is used to compute half the domain.<br /> <br /> Domain: [-3L;5L]x[0;2L]x[0;2L]<br /> <br /> Mesh : 450,000 cells<br /> <br /> Approximate value of y+ on solid surfaces : 30.<br /> <br /> <br /> ==='''Boundary Conditions CFD1'''===<br /> <br /> Inlet: turbulence level 0.5% with a mixing length of 5x10-3m.<br /> <br /> Outlet: constant pressure.<br /> <br /> Solid boundaries: wall functions<br /> <br /> Symmetry plane: symmetry<br /> <br /> Other boundaries: no details<br /> <br /> <br /> ==='''Application of Physical Models CFD1'''===<br /> <br /> Standard K-ε model with standard wall functions.<br /> <br /> <br /> ==='''Numerical Accuracy CFD1'''===<br /> <br /> Mesh refinement is performed until the drag reaches a constant value.<br /> <br /> Convection scheme : 2nd order.<br /> <br /> <br /> ==='''CFD Results CFD1'''===<br /> <br /> Friction lines, pressure iso-contours at the model surface, velocity vector fields, drag coefficient.<br /> <br /> =='''References CFD1'''==<br /> <br /> '''Modelling of stationnary three-dimensional separated flows around an Ahmed reference model.'''<br /> <br /> P. Gilliéron, F. Chometon, ESAIM proc., vol 7, 173-182, 1999<br /> <br /> <br /> =='''Simulation Case CFD2'''==<br /> <br /> ==='''Solution strategy CFD2'''===<br /> <br /> RANS modeling.<br /> <br /> Commercial FLUENT 5 code based on unstructured finite volume discretization.<br /> <br /> Reynolds number: 4.29x106 (see EXP1). Steady state computation.<br /> <br /> Slant angle: 30°.<br /> <br /> ==='''Computational Domain CFD2'''===<br /> <br /> Symmetry is used to compute half the domain. Stilts are included.<br /> <br /> Domain: no details.<br /> <br /> Mesh : 704,000 cells.<br /> <br /> y+ at the first grid point from the wall of order of 50 - 350.<br /> <br /> ==='''Boundary Conditions CFD2'''===<br /> <br /> No details.<br /> <br /> ==='''Application of Physical Models CFD2'''===<br /> <br /> - Standard k-ε model with non-equilibrium wall functions.<br /> <br /> - RSM (no details) with non-equilibrium wall functions.<br /> <br /> ==='''Numerical Accuracy CFD2'''===<br /> <br /> No details.<br /> <br /> ==='''CFD Results CFD2'''===<br /> <br /> Pathlines and velocities.<br /> <br /> Aerodynamic drag coefficient.<br /> <br /> =='''References CFD2'''==<br /> <br /> Advances in external-aero simulation of ground vehicles using the steady RANS equation.<br /> <br /> Makowski F.T and Kim S.E., SAE Conf 2000-01-0484<br /> <br /> <br /> =='''Simulation Case CFD3'''==<br /> <br /> ==='''Solution strategy CFD3'''===<br /> <br /> '''Large-eddy simulation.'''<br /> <br /> In house code PRICELES, based on unstructured second-order finite-element discretization.<br /> <br /> Reynolds number= 4.29 x106<br /> <br /> Slant angle: 28°.<br /> <br /> ==='''Computational Domain CFD3'''===<br /> <br /> Domain: [-3L;5L]x[-L;L]x[-LxL] (the ground plate is NOT included: the body is suspended in the middle of the domain).<br /> <br /> Mesh: 1.6x106 cells.<br /> <br /> y+ at the first grid point from the wall is about 80 (averaged value).<br /> <br /> ==='''Boundary Conditions CFD3'''===<br /> <br /> Inlet: constant velocity.<br /> <br /> Outlet: constant pressure conditions.<br /> <br /> Solid boundaries: wall functions<br /> <br /> Other boundaries : symmetry.<br /> <br /> ==='''Application of Physical Models CFD3'''===<br /> <br /> Sub-grid model: standard Smagorinsky.<br /> <br /> ==='''Numerical Accuracy CFD3'''===<br /> <br /> Second-order convection scheme and time marching (CFL number=3).<br /> <br /> ==='''CFD Results CFD3'''===<br /> <br /> '''Pressure, pressure coef., velocity, drag coef, Q-criterion contours, vorticity.'''<br /> <br /> =='''References CFD3'''==<br /> <br /> Large eddy simulation of an Ahmed reference model.<br /> <br /> R.J.A. Howard, M. Pourquie.<br /> <br /> Journal of Turbulence, 2002<br /> <br /> <br /> =='''Simulation Case CFD4'''==<br /> <br /> ==='''Solution strategy CFD4'''===<br /> <br /> RANS modelling.<br /> <br /> Commercial AVL SWIFT code, based on unstructured finite volume discretization.<br /> <br /> Reynolds number: 2.78x106 (see EXP2). Steady state computation.<br /> <br /> Slant angle: 25° and 35°.<br /> <br /> ==='''Computational Domain CFD4'''===<br /> <br /> Symmetry is used to compute half the domain.<br /> <br /> Domain: Inlet at -1.5L. No other details.<br /> <br /> Mesh : 530,000 cells.<br /> <br /> y+ on solid surfaces &lt; 100.<br /> <br /> ==='''Boundary Conditions CFD4'''===<br /> <br /> Inlet: interpolated experimental profile at –1.4L used at –1.5L.<br /> <br /> Solid boundaries: wall functions<br /> <br /> Symmetry plane: symmetry<br /> <br /> Other boundaries: no details<br /> <br /> ==='''Application of Physical Models CFD4'''===<br /> <br /> - Standard k-ε model with standard wall functions.<br /> <br /> - SSG Reynolds stress model with standard wall functions<br /> <br /> - Hybrid k-ε/Reynolds stress model (coefficient Cm of the k-ε model obtained from Reynolds stress transport equations) with standard wall functions<br /> <br /> ==='''Numerical Accuracy CFD4'''===<br /> <br /> Grid sensitivity study.<br /> <br /> Study of the influence of the convection scheme.<br /> <br /> ==='''CFD Results CFD4'''===<br /> <br /> Cp, velocity profiles in the boundary layer over the slant part.<br /> <br /> =='''References CFD4'''==<br /> <br /> B. Basara, S. Jakirlic, Flow Around a simplified car body (Ahmed body) : description of numerical methodology, in : S. Jakirlic, R. Jester-Zürker, C. Tropea, editors, 9th ERCOFTAC/IAHR/COST Workshop on Refined Turbulence Modelling, Oct. 4-5, 2001, Darmstadt University of Technology, Germany.<br /> <br /> <br /> =='''Simulation Case CFD5'''==<br /> <br /> =='''Solution strategy CFD5'''==<br /> <br /> RANS modelling.<br /> <br /> In-house code Saturne, based on unstructured finite volume discretization.<br /> <br /> Reynolds number: 2.78x106 (see EXP2). Steady state computation.<br /> <br /> Slant angle: 25° and 35°.<br /> <br /> ==='''Computational Domain CFD5'''===<br /> <br /> Full body (no symmetry used)<br /> <br /> Domain: no details<br /> <br /> Mesh : 300,000 cells<br /> <br /> y+ on solid surfaces : no details.<br /> <br /> ==='''Boundary Conditions CFD5'''===<br /> <br /> Inlet: no details.<br /> <br /> Solid boundaries: wall functions<br /> <br /> Other boundaries: no details<br /> <br /> ==='''Application of Physical Models CFD5'''===<br /> <br /> - Standard k-ε model with standard wall functions<br /> <br /> - Launder, Reece, Rodi (IP) Reynolds stress model with standard wall functions<br /> <br /> - Linearized production k-ε model with standard wall functions<br /> <br /> <br /> ==='''Numerical Accuracy CFD5'''===<br /> <br /> Convection scheme : 80% central differencing (2nd order), 20% upwind differencing (1st order).<br /> <br /> ==='''CFD Results CFD5'''===<br /> <br /> Cp, velocity profiles in the boundary layer over the slant part.<br /> <br /> Vector plots, turbulent energy contours, streamlines.<br /> <br /> =='''References CFD5'''==<br /> <br /> S. Tekam, D. Laurence, T. Buchal, Flow around the Ahmed body, in : S. Jakirlic, R. Jester-Zürker, C. Tropea, editors, 9th ERCOFTAC/ IAHR/ COST Workshop on Refined Turbulence Modelling, Oct. 4-5, 2001, Darmstadt University of Technology, Germany.<br /> <br /> <br /> =='''Simulation Case CFD6'''==<br /> <br /> ==='''Solution strategy CFD6'''===<br /> <br /> RANS modelling.<br /> <br /> Commercial FLUENT code, based on unstructured finite volume discretization.<br /> <br /> Reynolds number: 2.78x106 (see EXP2). Steady state computation.<br /> <br /> Slant angle: 25°.<br /> <br /> ==='''Computational Domain CFD6'''===<br /> <br /> Domain: no details<br /> <br /> Mesh : 2.3x106 cells<br /> <br /> y+ on solid surfaces : no details<br /> <br /> ==='''Boundary Conditions CFD6'''===<br /> <br /> Solid boundaries:<br /> <br /> - non-equilibrium wall functions for the k-ε model<br /> <br /> - no slip walls for the SST model<br /> <br /> <br /> <br /> Inlet, outlet and other boundaries: no details<br /> <br /> ==='''Application of Physical Models CFD6'''===<br /> <br /> - Realizable k-ε model with non-equilibrium wall functions<br /> <br /> - SST model<br /> <br /> ==='''Numerical Accuracy CFD6'''===<br /> <br /> No details<br /> <br /> ==='''CFD Results CFD6'''===<br /> <br /> Cp, velocity profiles in the boundary layer over the slant part.<br /> <br /> =='''References CFD6'''==<br /> <br /> M. Lanfrit, M. Braun, D. Cokljat, Contribution to case 9.4: Ahmed body, in : S. Jakirlic, R. Jester-Zürker, C. Tropea, editors, 9th ERCOFTAC/ IAHR/ COST Workshop on Refined Turbulence Modelling, Oct. 4-5, 2001, Darmstadt University of Technology, Germany.<br /> <br /> <br /> =='''Simulation Case CFD7'''==<br /> <br /> ==='''Solution strategy CFD7'''===<br /> <br /> RANS modelling in unsteady mode.<br /> <br /> In-house X-Stream code, based on finite volume solver for multi block structured non-orthogonal, curvilinear grid with collocated data arrangement. The convection terms are discretized using hybrid scheme with more than 60% central differencing. The diffusion terms are approximated with central differences. The SIMPLE method is used for the pressure-velocity coupling.<br /> <br /> Reynolds number: 2.78x106 (see EXP2).<br /> <br /> Slant angle: 35°<br /> <br /> ==='''Computational Domain CFD7'''===<br /> <br /> Full body (no symmetry condition used).<br /> <br /> Domain: [-2L;5L]x[-1.2;1.2L]x[0;1.3L]<br /> <br /> 9th ERCOFTAC workshop: 500,000 cells<br /> <br /> 10th ERCOFTAC workshop: 2 meshes: 490,000 and 820,000 cells (fine mesh used for the k-ε model only)<br /> <br /> Approximate value of y+ on solid surfaces:<br /> <br /> - 9th workshop: 60<br /> <br /> - 10th workshop: 17 (coarse mesh) and 11 (fine mesh).<br /> <br /> ==='''Boundary Conditions CFD7'''===<br /> <br /> Inlet: turbulence intensity=2,5%<br /> <br /> Solid boundaries: wall functions<br /> <br /> Outlet: no details<br /> <br /> Other boundaries: no details<br /> <br /> ==='''Application of Physical Models CFD7'''===<br /> <br /> 9th ERCOFTAC workshop:<br /> <br /> - Standard k-ε model with standard wall functions<br /> <br /> - SSG Reynolds stress model with standard wall functions<br /> <br /> - SSS Reynolds stress model with non-equilibrium wall functions<br /> <br /> - V2F model with wall functions<br /> <br /> - Elliptic blending model (Reynolds stress model) with wall functions<br /> <br /> <br /> <br /> 10th ERCOFTAC workshop:<br /> <br /> - Standard k-ε model with wall functions<br /> <br /> - V2F model with wall functions<br /> <br /> - SSG Reynolds stress model with modified ε equation (Hanjalic, Jakirlic) and standard wall functions<br /> <br /> ==='''Numerical Accuracy CFD7'''===<br /> <br /> Convection scheme : 60% 2nd order central differencing, 40% 1st order upwind differencing.<br /> <br /> ==='''CFD Results CFD7'''===<br /> <br /> Cp contours on the slant part, velocity profiles in the boundary layer over the slant part, vectors plots in 13 planes (see EXP2).<br /> <br /> ==''References CFD7'''==<br /> <br /> O. Ouhlous, W. Khier, Y. Liu, K. Hanjalic, in: S. Jakirlic, R. Jester-Zürker, C. Tropea, editors, 9th ERCOFTAC/ IAHR/ COST Workshop on Refined Turbulence Modelling, Oct. 4-5, 2001, Darmstadt University of Technology, Germany.<br /> <br /> <br /> <br /> M. Hadziabdic, K. Hanjalic, W. Khier, Y. Liu, O. Ouhlous, Flow around a simplified car body (Ahmed car model), in: R. Manceau, J.-P. Bonnet, editors, 10th ERCOFTAC (SIG-15)/IAHR/QNET-CFD Workshop on Refined Turbulence Modelling, Oct. 10-11, 2002, Laboratoire d’études aérodynamiques, UMR CNRS 6609, Université de Poitiers, France.<br /> <br /> <br /> =='''Simulation Case CFD8'''==<br /> <br /> ==='''Solution strategy CFD8'''===<br /> <br /> RANS modelling.<br /> <br /> In-house code STREAM, which is a finite volume solver which uses a structured, non-orthogonal curvilinear, multi block grid and a fully collocated arrangement. The SIMPLE pressure correction method and Rie &amp; Chow interpolation are used to prevent unrealistic pressure fluctuations. The convection terms are discretized using an upwind scheme or a TVD scheme based on the third-order QUICK scheme.<br /> <br /> Reynolds number: 2.78x106 (see EXP2). Steady state computation.<br /> <br /> Slant angle: 25° and 35°.<br /> <br /> ==='''Computational Domain CFD8'''===<br /> <br /> Symmetry is used to compute half the domain. Stilts not included.<br /> <br /> Domain: [-2L;4L]x[0;L]x[0;L]<br /> <br /> Mesh : 300,000 cells<br /> <br /> Approximate value of y+ on solid surfaces : between 55 and 550.<br /> <br /> ==='''Boundary Conditions CFD8'''===<br /> <br /> Inlet:<br /> <br /> - U=38.51 m/s (based on the experimental profile at –1.4L in order to account for the flow deceleration in front of the body)<br /> <br /> - K=6.58x10-3 m2 s-2<br /> <br /> - nt/n=10 (influence tested)<br /> <br /> <br /> <br /> Outflow: zero gradients for all variables<br /> <br /> Solid boundaries: wall functions<br /> <br /> Symmetry plane: symmetry<br /> <br /> Other boundaries: symmetry<br /> <br /> ==='''Application of Physical Models CFD8'''===<br /> <br /> - Standard k-ε model with Yap correction and SCL wall functions (see below)<br /> <br /> - Standard k-ε model with Yap correction and UMIST-N wall functions<br /> <br /> - Linear realizable k-ε model with SCL wall functions<br /> <br /> - Linear realizable k-ε model with UMIST-A wall functions<br /> <br /> - Nonlinear k-ε model (Craft et al.) with SCL wall functions<br /> <br /> - Nonlinear k-ε model (Craft et al.) with UMIST-A wall functions<br /> <br /> <br /> <br /> Wall functions:<br /> <br /> - SCL = Simplified Chieng and Launder<br /> <br /> - UMIST-A = UMIST Analytical<br /> <br /> - UMIST-N = UMIST Numerical<br /> <br /> ==='''Numerical Accuracy CFD8'''===<br /> <br /> Convection scheme : 3rd order Quick scheme (UMIST) or 1st order upwind scheme in case of numerical instability.<br /> <br /> Tests were made to assess iteration convergence. Some unsteady calculations were made too. A coarser grid was used to obtain some information on grid dependency.<br /> <br /> ==='''CFD Results CFD8'''===<br /> <br /> Cp contours on the slant part, velocity profiles in the boundary layer over the slant part, vectors plots in 13 planes (see EXP2).<br /> <br /> =='''References CFD8'''==<br /> <br /> T.J. Craft, S.E. Gant, H. Iacovides, B.E. Launder, C.M.E. Robinson, Computational methods applied to the study of flow around a simplified “Ahmed” car body, in: R. Manceau, J.-P. Bonnet, editors, 10th ERCOFTAC (SIG-15)/IAHR/QNET-CFD Workshop on Refined Turbulence Modelling, Oct. 10-11, 2002, Laboratoire d’études aérodynamiques, UMR CNRS 6609, Université de Poitiers, France.<br /> <br /> <br /> =='''Simulation Case CFD9'''==<br /> <br /> ==='''Solution strategy CFD9'''===<br /> <br /> LES.<br /> <br /> In-house code LESOCC2, based on block-structured finite volume discretization. A collocated cell arrangement was used employing the Rhie and Chow momentum interpolation procedure. The SIMPLE scheme was used for the pressure-velocity coupling, and the pressure correction equation was solved using the SIP method. Fluxes were discretized in space using a second order central difference scheme. The equations were integrated in time using a second order Runge Kutta scheme with an adaptive time step, employing a maximum CFL number of 0.6.<br /> <br /> Reynolds number: 2.78x106 (see EXP2).<br /> <br /> Slant angle: 25°.<br /> <br /> ==='''Computational Domain CFD9'''===<br /> <br /> Domain: [-2.2L;4.8L]x[-0.9L;0.9L]x[0;1.35L]. Ground plate and stilts included.<br /> <br /> Mesh :18.5x106 cells<br /> <br /> y+ on solid surfaces : no details<br /> <br /> ==='''Boundary Conditions CFD9'''===<br /> <br /> Inlet: constant velocity<br /> <br /> Outlet: convective outlet.<br /> <br /> Solid boundaries: wall functions<br /> <br /> Other boundaries: slip walls<br /> <br /> ==='''Application of Physical Models CFD9'''===<br /> <br /> Subgrid scale model: Smagorinky<br /> <br /> ==='''Numerical Accuracy CFD9'''===<br /> <br /> 2nd order convection scheme and time marching (CFL number &lt; 0.6)<br /> <br /> ==='''CFD Results CFD9'''===<br /> <br /> Cp contours on the slant part, velocity profiles in the boundary layer over the slant part, vectors plots in 13 planes (see EXP2).<br /> <br /> =='''References CFD9'''==<br /> <br /> C. Hinterberger, M. Garcia-Villalba, W. Rodi, Flow around a simplified car body. LES with wall functions, in: R. Manceau, J.-P. Bonnet, editors, 10th ERCOFTAC (SIG-15)/IAHR/QNET-CFD Workshop on Refined Turbulence Modelling, Oct. 10-11, 2002, Laboratoire d’études aérodynamiques, UMR CNRS 6609, Université de Poitiers, France.<br /> <br /> <br /> =='''Simulation Case CFD10'''==<br /> <br /> ==='''Solution strategy CFD10'''===<br /> <br /> RANS modelling.<br /> <br /> Commercial HEXANS CFD code, based on unstructured finite volume discretization. The convective fluxes are discretized using a centered scheme with 2nd and 4th order artificial dissipation. Diffusive fluxes are computed on pyramidal elements. The equations are integrated in time using the explicit Runge Kutta scheme. Local time stepping, multi grid and low-mach number preconditioning are used to accelerate the convergence to steady state. A mesh adaptation procedure is used in which the grid cells are refined by splitting it in 2, 4 or 8 subcells. The mesh adaptation is governed by criteria based on the flow physics, geometry or error estimates.<br /> <br /> Reynolds number: 2.78x106 (see EXP2). Steady state computation.<br /> <br /> Slant angle: 25°.<br /> <br /> ==='''Computational Domain CFD10'''===<br /> <br /> Symmetry is used to compute half the domain. Ground plate included, no stilts.<br /> <br /> Domain: [-2L;5L]x[0;0.9L]x[0;1.35L]<br /> <br /> Final Mesh : 815,000 cells<br /> <br /> Approximate value of y+ on solid surfaces : 1<br /> <br /> ==='''Boundary Conditions CFD10'''===<br /> <br /> Inflow: turbulence level 1%. nt/n = 1.<br /> <br /> Solid boundaries: no-slip walls<br /> <br /> Symmetry plane: symmetry<br /> <br /> Other boundaries: no details<br /> <br /> ==='''Application of Physical Models CFD10'''===<br /> <br /> Low-Reynolds number K-ε model (Yang-Shih).<br /> <br /> ==='''Numerical Accuracy CFD10'''===<br /> <br /> Mesh adaptation applied.<br /> <br /> Convection scheme : 2nd order.<br /> <br /> ==='''CFD Results CFD10'''===<br /> <br /> Cp contours on the slant part, velocity profiles in the boundary layer over the slant part, vectors plots in 13 planes (see EXP2).<br /> <br /> =='''References CFD10'''==<br /> <br /> B. Leonard, Ch. Hirsch, K. Kovalev, M. Elsden, K. Hillewaert, A. Patel, Flow around a simplified car body (Ahmed body), in: R. Manceau, J.-P. Bonnet, editors, 10th ERCOFTAC (SIG-15)/IAHR/QNET-CFD Workshop on Refined Turbulence Modelling, Oct. 10-11, 2002, Laboratoire d’études aérodynamiques, UMR CNRS 6609, Université de Poitiers, France.<br /> <br /> <br /> =='''Simulation Case CFD11'''==<br /> <br /> ==='''Solution strategy CFD11'''===<br /> <br /> RANS modelling.<br /> <br /> Commercial CFX-5 code, based on an unstructured, vertex based finite volume method. Co-located variables are used. The solver is second order accurate in space and time. The Rhie-Chow velocity pressure coupling is used. An implicit solver with algebraic multi grid is used to converge the equations to steady state.<br /> <br /> Reynolds number: 2.78x106 (see EXP2). Transient computation (steady solution obtained).<br /> <br /> Slant angle: 25° and 35°.<br /> <br /> ==='''Computational Domain CFD11'''===<br /> <br /> Symmetry is used to compute half the domain. No stilts included.<br /> <br /> Domain: [-3L;6L]x[0;0.9L]x[0;1.15L]<br /> <br /> The ground plate starts 2L in front of the body in order that the boundary layer approaching the body matches the experimental profile.<br /> <br /> Mesh : 2,5x106 cells<br /> <br /> Approximate value of y+ on solid surfaces : 1<br /> <br /> ==='''Boundary Conditions CFD11'''===<br /> <br /> Inlet: turbulence intensity=1%, nt/n=1.<br /> <br /> Solid boundaries:<br /> <br /> - SST model: no slip walls<br /> <br /> - Others: scalable wall functions<br /> <br /> Outlet: constant pressure<br /> <br /> Other boundaries: opening boundary conditions.<br /> <br /> ==='''Application of Physical Models CFD11'''===<br /> <br /> - Standard k-ε model with scalable wall functions<br /> <br /> - SST model<br /> <br /> - SSG Reynolds stress model with scalable wall functions<br /> <br /> ==='''Numerical Accuracy CFD11'''===<br /> <br /> Convection scheme: 2nd order.<br /> <br /> Studies of the influence of the following parameters are performed:<br /> <br /> Mesh refinement, formulation of the boundary conditions (opening vs. slip walls), advection scheme.<br /> <br /> ==='''CFD Results CFD11'''===<br /> <br /> The same quantities (except for triple correlations) as for experiment EXP2 are available in the Knowledge Base : results for the mean velocities U, V, W, Reynolds stresses [[Image:Image23.gif]] [[Image:Image24.gif]] [[Image:Image25.gif]] [[Image:Image26.gif]] [[Image:Image27.gif]] in some planes and profiles in the boundary layer above the slant part:<br /> <br /> <br /> <br /> <br /> '''k-epsilon model'''<br /> <br /> 25° slant angle:<br /> <br /> planes:<br /> &lt;span class=&quot;plainlinks&quot;&gt;[{{filepath:CFD11_KEPS_Ahmed_25_y=0.dat}} y=0]&lt;/span&gt;;<br /> &lt;span class=&quot;plainlinks&quot;&gt;[{{filepath:CFD11_KEPS_Ahmed_25_y=100.dat}} y=100]&lt;/span&gt;; <br /> &lt;span class=&quot;plainlinks&quot;&gt;[{{filepath:CFD11_KEPS_Ahmed_25_y=180.dat}} y=180]&lt;/span&gt;;<br /> <br /> &lt;span class=&quot;plainlinks&quot;&gt;[{{filepath:CFD11_KEPS_Ahmed_25_y=195.dat}} y=195]&lt;/span&gt;;<br /> &lt;span class=&quot;plainlinks&quot;&gt;[{{filepath:CFD11_KEPS_Ahmed_25_z=360.dat}} z=360]&lt;/span&gt;<br /> <br /> &lt;span class=&quot;plainlinks&quot;&gt;[{{filepath:CFD11_KEPS_Ahmed_25_x=-794.dat}} x=-794]&lt;/span&gt;;<br /> &lt;span class=&quot;plainlinks&quot;&gt;[{{filepath:CFD11_KEPS_Ahmed_25_x=-178.dat}} x=-178]&lt;/span&gt;;<br /> &lt;span class=&quot;plainlinks&quot;&gt;[{{filepath:CFD11_KEPS_Ahmed_25_x=-138.dat}} x=-138]&lt;/span&gt;;<br /> &lt;span class=&quot;plainlinks&quot;&gt;[{{filepath:CFD11_KEPS_Ahmed_25_x=-88.dat}} x=-88]&lt;/span&gt;;<br /> &lt;span class=&quot;plainlinks&quot;&gt;[{{filepath:CFD11_KEPS_Ahmed_25_x=-38.dat}} x=-38]&lt;/span&gt;;<br /> &lt;span class=&quot;plainlinks&quot;&gt;[{{filepath:CFD11_KEPS_Ahmed_25_x=0.dat}} x=0]&lt;/span&gt;;<br /> &lt;span class=&quot;plainlinks&quot;&gt;[{{filepath:CFD11_KEPS_Ahmed_25_x=80.dat}} x=80]&lt;/span&gt;;<br /> &lt;span class=&quot;plainlinks&quot;&gt;[{{filepath:CFD11_KEPS_Ahmed_25_x=200.dat}} x=200]&lt;/span&gt;;<br /> &lt;span class=&quot;plainlinks&quot;&gt;[{{filepath:CFD11_KEPS_Ahmed_25_x=500.dat}} x=500]&lt;/span&gt;<br /> <br /> profiles in the boundary layer:<br /> &lt;span class=&quot;plainlinks&quot;&gt;[{{filepath:CFD11_KEPS_Ahmed_25_BL_x=-243.dat}} x=-243]&lt;/span&gt;,<br /> &lt;span class=&quot;plainlinks&quot;&gt;[{{filepath:CFD11_KEPS_Ahmed_25_BL_x=-223.dat}} -223]&lt;/span&gt;,<br /> &lt;span class=&quot;plainlinks&quot;&gt;[{{filepath:CFD11_KEPS_Ahmed_25_BL_x=-203.dat}} -203]&lt;/span&gt;,<br /> &lt;span class=&quot;plainlinks&quot;&gt;[{{filepath:CFD11_KEPS_Ahmed_25_BL_x=-183.dat}} -183]&lt;/span&gt;,<br /> &lt;span class=&quot;plainlinks&quot;&gt;[{{filepath:CFD11_KEPS_Ahmed_25_BL_x=-163.dat}} -163]&lt;/span&gt;,<br /> &lt;span class=&quot;plainlinks&quot;&gt;[{{filepath:CFD11_KEPS_Ahmed_25_BL_x=-143.dat}} -143]&lt;/span&gt;,<br /> &lt;span class=&quot;plainlinks&quot;&gt;[{{filepath:CFD11_KEPS_Ahmed_25_BL_x=-123.dat}} -123]&lt;/span&gt;,<br /> &lt;span class=&quot;plainlinks&quot;&gt;[{{filepath:CFD11_KEPS_Ahmed_25_BL_x=-103.dat}} -103]&lt;/span&gt;,<br /> &lt;span class=&quot;plainlinks&quot;&gt;[{{filepath:CFD11_KEPS_Ahmed_25_BL_x=-83.dat}} -83]&lt;/span&gt;,<br /> &lt;span class=&quot;plainlinks&quot;&gt;[{{filepath:CFD11_KEPS_Ahmed_25_BL_x=-63.dat}} -63]&lt;/span&gt;,<br /> &lt;span class=&quot;plainlinks&quot;&gt;[{{filepath:CFD11_KEPS_Ahmed_25_BL_x=-43.dat}} -43]&lt;/span&gt;,<br /> &lt;span class=&quot;plainlinks&quot;&gt;[{{filepath:CFD11_KEPS_Ahmed_25_BL_x=-23.dat}} -23]&lt;/span&gt;,<br /> &lt;span class=&quot;plainlinks&quot;&gt;[{{filepath:CFD11_KEPS_Ahmed_25_BL_x=-3.dat}} -3]&lt;/span&gt;<br /> <br /> Pressure coefficients on the rear of the body:<br /> &lt;span class=&quot;plainlinks&quot;&gt;[{{filepath:CFD11_KEPS_Ahmed_25_Cp.dat}} Cp]&lt;/span&gt;<br /> <br /> <br /> <br /> 35° slant angle:<br /> <br /> planes:<br /> &lt;span class=&quot;plainlinks&quot;&gt;[{{filepath:CFD11_KEPS_Ahmed_35_y=0.dat}} y=0]&lt;/span&gt;;<br /> &lt;span class=&quot;plainlinks&quot;&gt;[{{filepath:CFD11_KEPS_Ahmed_35_y=100.dat}} y=100]&lt;/span&gt;; <br /> &lt;span class=&quot;plainlinks&quot;&gt;[{{filepath:CFD11_KEPS_Ahmed_35_y=180.dat}} y=180]&lt;/span&gt;;<br /> <br /> &lt;span class=&quot;plainlinks&quot;&gt;[{{filepath:CFD11_KEPS_Ahmed_35_y=195.dat}} y=195]&lt;/span&gt;;<br /> &lt;span class=&quot;plainlinks&quot;&gt;[{{filepath:CFD11_KEPS_Ahmed_35_z=360.dat}} z=360]&lt;/span&gt;<br /> <br /> &lt;span class=&quot;plainlinks&quot;&gt;[{{filepath:CFD11_KEPS_Ahmed_35_x=-794.dat}} x=-794]&lt;/span&gt;;<br /> &lt;span class=&quot;plainlinks&quot;&gt;[{{filepath:CFD11_KEPS_Ahmed_35_x=-178.dat}} x=-178]&lt;/span&gt;;<br /> &lt;span class=&quot;plainlinks&quot;&gt;[{{filepath:CFD11_KEPS_Ahmed_35_x=-138.dat}} x=-138]&lt;/span&gt;;<br /> &lt;span class=&quot;plainlinks&quot;&gt;[{{filepath:CFD11_KEPS_Ahmed_35_x=-88.dat}} x=-88]&lt;/span&gt;;<br /> &lt;span class=&quot;plainlinks&quot;&gt;[{{filepath:CFD11_KEPS_Ahmed_35_x=-38.dat}} x=-38]&lt;/span&gt;;<br /> &lt;span class=&quot;plainlinks&quot;&gt;[{{filepath:CFD11_KEPS_Ahmed_35_x=0.dat}} x=0]&lt;/span&gt;;<br /> &lt;span class=&quot;plainlinks&quot;&gt;[{{filepath:CFD11_KEPS_Ahmed_35_x=80.dat}} x=80]&lt;/span&gt;;<br /> &lt;span class=&quot;plainlinks&quot;&gt;[{{filepath:CFD11_KEPS_Ahmed_35_x=200.dat}} x=200]&lt;/span&gt;;<br /> &lt;span class=&quot;plainlinks&quot;&gt;[{{filepath:CFD11_KEPS_Ahmed_35_x=500.dat}} x=500]&lt;/span&gt;<br /> <br /> profiles in the boundary layer:<br /> &lt;span class=&quot;plainlinks&quot;&gt;[{{filepath:CFD11_KEPS_Ahmed_35_BL_x=-243.dat}} x=-243]&lt;/span&gt;,<br /> &lt;span class=&quot;plainlinks&quot;&gt;[{{filepath:CFD11_KEPS_Ahmed_35_BL_x=-223.dat}} -223]&lt;/span&gt;,<br /> &lt;span class=&quot;plainlinks&quot;&gt;[{{filepath:CFD11_KEPS_Ahmed_35_BL_x=-203.dat}} -203]&lt;/span&gt;,<br /> &lt;span class=&quot;plainlinks&quot;&gt;[{{filepath:CFD11_KEPS_Ahmed_35_BL_x=-183.dat}} -183]&lt;/span&gt;,<br /> &lt;span class=&quot;plainlinks&quot;&gt;[{{filepath:CFD11_KEPS_Ahmed_35_BL_x=-163.dat}} -163]&lt;/span&gt;,<br /> &lt;span class=&quot;plainlinks&quot;&gt;[{{filepath:CFD11_KEPS_Ahmed_35_BL_x=-143.dat}} -143]&lt;/span&gt;,<br /> &lt;span class=&quot;plainlinks&quot;&gt;[{{filepath:CFD11_KEPS_Ahmed_35_BL_x=-123.dat}} -123]&lt;/span&gt;,<br /> &lt;span class=&quot;plainlinks&quot;&gt;[{{filepath:CFD11_KEPS_Ahmed_35_BL_x=-103.dat}} -103]&lt;/span&gt;,<br /> &lt;span class=&quot;plainlinks&quot;&gt;[{{filepath:CFD11_KEPS_Ahmed_35_BL_x=-83.dat}} -83]&lt;/span&gt;,<br /> &lt;span class=&quot;plainlinks&quot;&gt;[{{filepath:CFD11_KEPS_Ahmed_35_BL_x=-63.dat}} -63]&lt;/span&gt;,<br /> &lt;span class=&quot;plainlinks&quot;&gt;[{{filepath:CFD11_KEPS_Ahmed_35_BL_x=-43.dat}} -43]&lt;/span&gt;,<br /> &lt;span class=&quot;plainlinks&quot;&gt;[{{filepath:CFD11_KEPS_Ahmed_35_BL_x=-23.dat}} -23]&lt;/span&gt;,<br /> &lt;span class=&quot;plainlinks&quot;&gt;[{{filepath:CFD11_KEPS_Ahmed_35_BL_x=-3.dat}} -3]&lt;/span&gt;<br /> <br /> Pressure coefficients on the rear of the body:<br /> &lt;span class=&quot;plainlinks&quot;&gt;[{{filepath:CFD11_KEPS_Ahmed_35_Cp.dat}} Cp]&lt;/span&gt;<br /> <br /> <br /> <br /> '''SST model'''<br /> <br /> 25° slant angle:<br /> <br /> planes:<br /> &lt;span class=&quot;plainlinks&quot;&gt;[{{filepath:CFD11_SST_Ahmed_25_y=0.dat}} y=0]&lt;/span&gt;;<br /> &lt;span class=&quot;plainlinks&quot;&gt;[{{filepath:CFD11_SST_Ahmed_25_y=100.dat}} y=100]&lt;/span&gt;; <br /> &lt;span class=&quot;plainlinks&quot;&gt;[{{filepath:CFD11_SST_Ahmed_25_y=180.dat}} y=180]&lt;/span&gt;;<br /> <br /> &lt;span class=&quot;plainlinks&quot;&gt;[{{filepath:CFD11_SST_Ahmed_25_y=195.dat}} y=195]&lt;/span&gt;;<br /> &lt;span class=&quot;plainlinks&quot;&gt;[{{filepath:CFD11_SST_Ahmed_25_z=360.dat}} z=360]&lt;/span&gt;<br /> <br /> &lt;span class=&quot;plainlinks&quot;&gt;[{{filepath:CFD11_SST_Ahmed_25_x=-794.dat}} x=-794]&lt;/span&gt;;<br /> &lt;span class=&quot;plainlinks&quot;&gt;[{{filepath:CFD11_SST_Ahmed_25_x=-178.dat}} x=-178]&lt;/span&gt;;<br /> &lt;span class=&quot;plainlinks&quot;&gt;[{{filepath:CFD11_SST_Ahmed_25_x=-138.dat}} x=-138]&lt;/span&gt;;<br /> &lt;span class=&quot;plainlinks&quot;&gt;[{{filepath:CFD11_SST_Ahmed_25_x=-88.dat}} x=-88]&lt;/span&gt;;<br /> &lt;span class=&quot;plainlinks&quot;&gt;[{{filepath:CFD11_SST_Ahmed_25_x=-38.dat}} x=-38]&lt;/span&gt;;<br /> &lt;span class=&quot;plainlinks&quot;&gt;[{{filepath:CFD11_SST_Ahmed_25_x=0.dat}} x=0]&lt;/span&gt;;<br /> &lt;span class=&quot;plainlinks&quot;&gt;[{{filepath:CFD11_SST_Ahmed_25_x=80.dat}} x=80]&lt;/span&gt;;<br /> &lt;span class=&quot;plainlinks&quot;&gt;[{{filepath:CFD11_SST_Ahmed_25_x=200.dat}} x=200]&lt;/span&gt;;<br /> &lt;span class=&quot;plainlinks&quot;&gt;[{{filepath:CFD11_SST_Ahmed_25_x=500.dat}} x=500]&lt;/span&gt;<br /> <br /> profiles in the boundary layer:<br /> &lt;span class=&quot;plainlinks&quot;&gt;[{{filepath:CFD11_SST_Ahmed_25_BL_x=-243.dat}} x=-243]&lt;/span&gt;,<br /> &lt;span class=&quot;plainlinks&quot;&gt;[{{filepath:CFD11_SST_Ahmed_25_BL_x=-223.dat}} -223]&lt;/span&gt;,<br /> &lt;span class=&quot;plainlinks&quot;&gt;[{{filepath:CFD11_SST_Ahmed_25_BL_x=-203.dat}} -203]&lt;/span&gt;,<br /> &lt;span class=&quot;plainlinks&quot;&gt;[{{filepath:CFD11_SST_Ahmed_25_BL_x=-183.dat}} -183]&lt;/span&gt;,<br /> &lt;span class=&quot;plainlinks&quot;&gt;[{{filepath:CFD11_SST_Ahmed_25_BL_x=-163.dat}} -163]&lt;/span&gt;,<br /> &lt;span class=&quot;plainlinks&quot;&gt;[{{filepath:CFD11_SST_Ahmed_25_BL_x=-143.dat}} -143]&lt;/span&gt;,<br /> &lt;span class=&quot;plainlinks&quot;&gt;[{{filepath:CFD11_SST_Ahmed_25_BL_x=-123.dat}} -123]&lt;/span&gt;,<br /> -103,<br /> &lt;span class=&quot;plainlinks&quot;&gt;[{{filepath:CFD11_SST_Ahmed_25_BL_x=-83.dat}} -83]&lt;/span&gt;,<br /> &lt;span class=&quot;plainlinks&quot;&gt;[{{filepath:CFD11_SST_Ahmed_25_BL_x=-63.dat}} -63]&lt;/span&gt;,<br /> &lt;span class=&quot;plainlinks&quot;&gt;[{{filepath:CFD11_SST_Ahmed_25_BL_x=-43.dat}} -43]&lt;/span&gt;,<br /> &lt;span class=&quot;plainlinks&quot;&gt;[{{filepath:CFD11_SST_Ahmed_25_BL_x=-23.dat}} -23]&lt;/span&gt;,<br /> &lt;span class=&quot;plainlinks&quot;&gt;[{{filepath:CFD11_SST_Ahmed_25_BL_x=-3.dat}} -3]&lt;/span&gt;<br /> <br /> Pressure coefficients on the rear of the body:<br /> &lt;span class=&quot;plainlinks&quot;&gt;[{{filepath:CFD11_SST_Ahmed_25_Cp.dat}} Cp]&lt;/span&gt;<br /> <br /> <br /> <br /> 35° slant angle:<br /> planes:<br /> &lt;span class=&quot;plainlinks&quot;&gt;[{{filepath:CFD11_SST_Ahmed_35_y=0.dat}} y=0]&lt;/span&gt;;<br /> &lt;span class=&quot;plainlinks&quot;&gt;[{{filepath:CFD11_SST_Ahmed_35_y=100.dat}} y=100]&lt;/span&gt;; <br /> &lt;span class=&quot;plainlinks&quot;&gt;[{{filepath:CFD11_SST_Ahmed_35_y=180.dat}} y=180]&lt;/span&gt;;<br /> <br /> &lt;span class=&quot;plainlinks&quot;&gt;[{{filepath:CFD11_SST_Ahmed_35_y=195.dat}} y=195]&lt;/span&gt;;<br /> z=360<br /> <br /> &lt;span class=&quot;plainlinks&quot;&gt;[{{filepath:CFD11_SST_Ahmed_35_x=-178.dat}} x=-178]&lt;/span&gt;;<br /> &lt;span class=&quot;plainlinks&quot;&gt;[{{filepath:CFD11_SST_Ahmed_35_x=-138.dat}} x=-138]&lt;/span&gt;;<br /> &lt;span class=&quot;plainlinks&quot;&gt;[{{filepath:CFD11_SST_Ahmed_35_x=-88.dat}} x=-88]&lt;/span&gt;;<br /> &lt;span class=&quot;plainlinks&quot;&gt;[{{filepath:CFD11_SST_Ahmed_35_x=-38.dat}} x=-38]&lt;/span&gt;;<br /> &lt;span class=&quot;plainlinks&quot;&gt;[{{filepath:CFD11_SST_Ahmed_35_x=0.dat}} x=0]&lt;/span&gt;;<br /> &lt;span class=&quot;plainlinks&quot;&gt;[{{filepath:CFD11_SST_Ahmed_35_x=80.dat}} x=80]&lt;/span&gt;;<br /> &lt;span class=&quot;plainlinks&quot;&gt;[{{filepath:CFD11_SST_Ahmed_35_x=200.dat}} x=200]&lt;/span&gt;;<br /> &lt;span class=&quot;plainlinks&quot;&gt;[{{filepath:CFD11_SST_Ahmed_35_x=500.dat}} x=500]&lt;/span&gt;<br /> <br /> profiles in the boundary layer:<br /> &lt;span class=&quot;plainlinks&quot;&gt;[{{filepath:CFD11_SST_Ahmed_35_BL_x=-243.dat}} x=-243]&lt;/span&gt;,<br /> &lt;span class=&quot;plainlinks&quot;&gt;[{{filepath:CFD11_SST_Ahmed_35_BL_x=-223.dat}} -223]&lt;/span&gt;,<br /> &lt;span class=&quot;plainlinks&quot;&gt;[{{filepath:CFD11_SST_Ahmed_35_BL_x=-203.dat}} -203]&lt;/span&gt;,<br /> &lt;span class=&quot;plainlinks&quot;&gt;[{{filepath:CFD11_SST_Ahmed_35_BL_x=-183.dat}} -183]&lt;/span&gt;,<br /> &lt;span class=&quot;plainlinks&quot;&gt;[{{filepath:CFD11_SST_Ahmed_35_BL_x=-163.dat}} -163]&lt;/span&gt;,<br /> &lt;span class=&quot;plainlinks&quot;&gt;[{{filepath:CFD11_SST_Ahmed_35_BL_x=-143.dat}} -143]&lt;/span&gt;,<br /> &lt;span class=&quot;plainlinks&quot;&gt;[{{filepath:CFD11_SST_Ahmed_35_BL_x=-123.dat}} -123]&lt;/span&gt;,<br /> &lt;span class=&quot;plainlinks&quot;&gt;[{{filepath:CFD11_SST_Ahmed_35_BL_x=-103.dat}} -103]&lt;/span&gt;,<br /> &lt;span class=&quot;plainlinks&quot;&gt;[{{filepath:CFD11_SST_Ahmed_35_BL_x=-83.dat}} -83]&lt;/span&gt;,<br /> &lt;span class=&quot;plainlinks&quot;&gt;[{{filepath:CFD11_SST_Ahmed_35_BL_x=-63.dat}} -63]&lt;/span&gt;,<br /> &lt;span class=&quot;plainlinks&quot;&gt;[{{filepath:CFD11_SST_Ahmed_35_BL_x=-43.dat}} -43]&lt;/span&gt;,<br /> &lt;span class=&quot;plainlinks&quot;&gt;[{{filepath:CFD11_SST_Ahmed_35_BL_x=-23.dat}} -23]&lt;/span&gt;,<br /> &lt;span class=&quot;plainlinks&quot;&gt;[{{filepath:CFD11_SST_Ahmed_35_BL_x=-3.dat}} -3]&lt;/span&gt;<br /> <br /> Pressure coefficients on the rear of the body:<br /> &lt;span class=&quot;plainlinks&quot;&gt;[{{filepath:CFD11_SST_Ahmed_35_Cp.dat}} Cp]&lt;/span&gt;<br /> <br /> =='''References CFD11'''==<br /> <br /> L. Durand, M. Kuntz, F. Menter, Validation of CFX-5 for the Ahmed car body (synopsis), in: R. Manceau, J.-P. Bonnet, editors, 10th ERCOFTAC (SIG-15)/IAHR/QNET-CFD Workshop on Refined Turbulence Modelling, Oct. 10-11, 2002, Laboratoire d’études aérodynamiques, UMR CNRS 6609, Université de Poitiers, France.<br /> <br /> <br /> <br /> L. Durand, M. Kuntz, F. Menter, Validation of CFX-5 for the Ahmed car body, CFX Validation report (florian.menter@ansys.com)<br /> <br /> <br /> =='''Simulation Case CFD12'''==<br /> <br /> ==='''Solution strategy CFD12'''===<br /> <br /> RANS modelling.<br /> <br /> In-house code CFL3D, compressible flow solver employing multi block structured grids. An upwind finite volume formulation is used for the space discretization. An implicit approximate factorization method is used to integrate the equations in time. Local time stepping, grid sequencing, multi grid and low Mach number preconditioning are used to accelerate convergence to steady state.<br /> <br /> Reynolds number: 2.78x106 (see EXP2). Steady state computation.<br /> <br /> Slant angle: 25° and 35°.<br /> <br /> ==='''Computational Domain CFD12'''===<br /> <br /> Symmetry is used to compute half the domain. No stilts included.<br /> <br /> Domain: [-3L;6L]x[0;0.9L]x[0;1.15L]<br /> <br /> Mesh : 1.3x106 cells<br /> <br /> Approximate value of y+ on solid surfaces : 1.5<br /> <br /> ==='''Boundary Conditions CFD12'''===<br /> <br /> Inlet: no details<br /> <br /> Solid boundaries: no-slip walls<br /> <br /> Symmetry plane: symmetry<br /> <br /> Other boundaries: farfield Riemann-invariant conditions<br /> <br /> ==='''Application of Physical Models CFD12'''===<br /> <br /> - SST model<br /> <br /> - Explicit Algebraic Stress Model with ω-equation<br /> <br /> ==='''Numerical Accuracy CFD12'''===<br /> <br /> Convection scheme : 1st order.<br /> <br /> ==='''CFD Results CFD12'''===<br /> <br /> The same quantities (except for triple correlations) as for experiment EXP2 are available in the Knowledge Base : results for the mean velocities U, V, W, Reynolds stresses [[Image:Image23.gif]] [[Image:Image24.gif]] [[Image:Image25.gif]] [[Image:Image26.gif]] [[Image:Image27.gif]] in some planes and profiles in the boundary layer above the slant part:<br /> <br /> <br /> <br /> '''SST model'''<br /> <br /> 25° slant angle:<br /> <br /> planes:<br /> &lt;span class=&quot;plainlinks&quot;&gt;[{{filepath:CFD12_SST_Ahmed_25_y=0.dat}} y=0]&lt;/span&gt;;<br /> &lt;span class=&quot;plainlinks&quot;&gt;[{{filepath:CFD12_SST_Ahmed_25_y=100.dat}} y=100]&lt;/span&gt;; <br /> &lt;span class=&quot;plainlinks&quot;&gt;[{{filepath:CFD12_SST_Ahmed_25_y=180.dat}} y=180]&lt;/span&gt;;<br /> <br /> &lt;span class=&quot;plainlinks&quot;&gt;[{{filepath:CFD12_SST_Ahmed_25_y=195.dat}} y=195]&lt;/span&gt;;<br /> &lt;span class=&quot;plainlinks&quot;&gt;[{{filepath:CFD12_SST_Ahmed_25_z=360.dat}} z=360]&lt;/span&gt;<br /> <br /> &lt;span class=&quot;plainlinks&quot;&gt;[{{filepath:CFD12_SST_Ahmed_25_x=-794.dat}} x=-794]&lt;/span&gt;;<br /> &lt;span class=&quot;plainlinks&quot;&gt;[{{filepath:CFD12_SST_Ahmed_25_x=-178.dat}} x=-178]&lt;/span&gt;;<br /> &lt;span class=&quot;plainlinks&quot;&gt;[{{filepath:CFD12_SST_Ahmed_25_x=-138.dat}} x=-138]&lt;/span&gt;;<br /> &lt;span class=&quot;plainlinks&quot;&gt;[{{filepath:CFD12_SST_Ahmed_25_x=-88.dat}} x=-88]&lt;/span&gt;;<br /> &lt;span class=&quot;plainlinks&quot;&gt;[{{filepath:CFD12_SST_Ahmed_25_x=-38.dat}} x=-38]&lt;/span&gt;;<br /> &lt;span class=&quot;plainlinks&quot;&gt;[{{filepath:CFD12_SST_Ahmed_25_x=0.dat}} x=0]&lt;/span&gt;;<br /> &lt;span class=&quot;plainlinks&quot;&gt;[{{filepath:CFD12_SST_Ahmed_25_x=80.dat}} x=80]&lt;/span&gt;;<br /> &lt;span class=&quot;plainlinks&quot;&gt;[{{filepath:CFD12_SST_Ahmed_25_x=200.dat}} x=200]&lt;/span&gt;;<br /> &lt;span class=&quot;plainlinks&quot;&gt;[{{filepath:CFD12_SST_Ahmed_25_x=500.dat}} x=500]&lt;/span&gt;<br /> <br /> profiles in the boundary layer:<br /> &lt;span class=&quot;plainlinks&quot;&gt;[{{filepath:CFD12_SST_Ahmed_25_BL_x=-243.dat}} x=-243]&lt;/span&gt;,<br /> &lt;span class=&quot;plainlinks&quot;&gt;[{{filepath:CFD12_SST_Ahmed_25_BL_x=-223.dat}} -223]&lt;/span&gt;,<br /> &lt;span class=&quot;plainlinks&quot;&gt;[{{filepath:CFD12_SST_Ahmed_25_BL_x=-203.dat}} -203]&lt;/span&gt;,<br /> &lt;span class=&quot;plainlinks&quot;&gt;[{{filepath:CFD12_SST_Ahmed_25_BL_x=-183.dat}} -183]&lt;/span&gt;,<br /> &lt;span class=&quot;plainlinks&quot;&gt;[{{filepath:CFD12_SST_Ahmed_25_BL_x=-163.dat}} -163]&lt;/span&gt;,<br /> &lt;span class=&quot;plainlinks&quot;&gt;[{{filepath:CFD12_SST_Ahmed_25_BL_x=-143.dat}} -143]&lt;/span&gt;,<br /> &lt;span class=&quot;plainlinks&quot;&gt;[{{filepath:CFD12_SST_Ahmed_25_BL_x=-123.dat}} -123]&lt;/span&gt;,<br /> &lt;span class=&quot;plainlinks&quot;&gt;[{{filepath:CFD12_SST_Ahmed_25_BL_x=-103.dat}} -103]&lt;/span&gt;,<br /> &lt;span class=&quot;plainlinks&quot;&gt;[{{filepath:CFD12_SST_Ahmed_25_BL_x=-83.dat}} -83]&lt;/span&gt;,<br /> &lt;span class=&quot;plainlinks&quot;&gt;[{{filepath:CFD12_SST_Ahmed_25_BL_x=-63.dat}} -63]&lt;/span&gt;,<br /> &lt;span class=&quot;plainlinks&quot;&gt;[{{filepath:CFD12_SST_Ahmed_25_BL_x=-43.dat}} -43]&lt;/span&gt;,<br /> &lt;span class=&quot;plainlinks&quot;&gt;[{{filepath:CFD12_SST_Ahmed_25_BL_x=-23.dat}} -23]&lt;/span&gt;,<br /> &lt;span class=&quot;plainlinks&quot;&gt;[{{filepath:CFD12_SST_Ahmed_25_BL_x=-3.dat}} -3]&lt;/span&gt;<br /> <br /> Pressure coefficients on the rear of the body:<br /> &lt;span class=&quot;plainlinks&quot;&gt;[{{filepath:CFD12_SST_Ahmed_25_Cp.dat}} Cp]&lt;/span&gt;<br /> <br /> <br /> 35° slant angle:<br /> <br /> planes:<br /> &lt;span class=&quot;plainlinks&quot;&gt;[{{filepath:CFD12_SST_Ahmed_35_y=0.dat}} y=0]&lt;/span&gt;;<br /> &lt;span class=&quot;plainlinks&quot;&gt;[{{filepath:CFD12_SST_Ahmed_35_y=100.dat}} y=100]&lt;/span&gt;; <br /> &lt;span class=&quot;plainlinks&quot;&gt;[{{filepath:CFD12_SST_Ahmed_35_y=180.dat}} y=180]&lt;/span&gt;;<br /> <br /> &lt;span class=&quot;plainlinks&quot;&gt;[{{filepath:CFD12_SST_Ahmed_35_y=195.dat}} y=195]&lt;/span&gt;;<br /> &lt;span class=&quot;plainlinks&quot;&gt;[{{filepath:CFD12_SST_Ahmed_35_z=360.dat}} z=360]&lt;/span&gt;<br /> <br /> &lt;span class=&quot;plainlinks&quot;&gt;[{{filepath:CFD12_SST_Ahmed_35_x=-794.dat}} x=-794]&lt;/span&gt;;<br /> &lt;span class=&quot;plainlinks&quot;&gt;[{{filepath:CFD12_SST_Ahmed_35_x=-178.dat}} x=-178]&lt;/span&gt;;<br /> &lt;span class=&quot;plainlinks&quot;&gt;[{{filepath:CFD12_SST_Ahmed_35_x=-138.dat}} x=-138]&lt;/span&gt;;<br /> &lt;span class=&quot;plainlinks&quot;&gt;[{{filepath:CFD12_SST_Ahmed_35_x=-88.dat}} x=-88]&lt;/span&gt;;<br /> &lt;span class=&quot;plainlinks&quot;&gt;[{{filepath:CFD12_SST_Ahmed_35_x=-38.dat}} x=-38]&lt;/span&gt;;<br /> &lt;span class=&quot;plainlinks&quot;&gt;[{{filepath:CFD12_SST_Ahmed_35_x=0.dat}} x=0]&lt;/span&gt;;<br /> &lt;span class=&quot;plainlinks&quot;&gt;[{{filepath:CFD12_SST_Ahmed_35_x=80.dat}} x=80]&lt;/span&gt;;<br /> &lt;span class=&quot;plainlinks&quot;&gt;[{{filepath:CFD12_SST_Ahmed_35_x=200.dat}} x=200]&lt;/span&gt;;<br /> &lt;span class=&quot;plainlinks&quot;&gt;[{{filepath:CFD12_SST_Ahmed_35_x=500.dat}} x=500]&lt;/span&gt;<br /> <br /> profiles in the boundary layer:<br /> &lt;span class=&quot;plainlinks&quot;&gt;[{{filepath:CFD12_SST_Ahmed_35_BL_x=-243.dat}} x=-243]&lt;/span&gt;,<br /> &lt;span class=&quot;plainlinks&quot;&gt;[{{filepath:CFD12_SST_Ahmed_35_BL_x=-223.dat}} -223]&lt;/span&gt;,<br /> &lt;span class=&quot;plainlinks&quot;&gt;[{{filepath:CFD12_SST_Ahmed_35_BL_x=-203.dat}} -203]&lt;/span&gt;,<br /> &lt;span class=&quot;plainlinks&quot;&gt;[{{filepath:CFD12_SST_Ahmed_35_BL_x=-183.dat}} -183]&lt;/span&gt;,<br /> &lt;span class=&quot;plainlinks&quot;&gt;[{{filepath:CFD12_SST_Ahmed_35_BL_x=-163.dat}} -163]&lt;/span&gt;,<br /> &lt;span class=&quot;plainlinks&quot;&gt;[{{filepath:CFD12_SST_Ahmed_35_BL_x=-143.dat}} -143]&lt;/span&gt;,<br /> &lt;span class=&quot;plainlinks&quot;&gt;[{{filepath:CFD12_SST_Ahmed_35_BL_x=-123.dat}} -123]&lt;/span&gt;,<br /> &lt;span class=&quot;plainlinks&quot;&gt;[{{filepath:CFD12_SST_Ahmed_35_BL_x=-103.dat}} -103]&lt;/span&gt;,<br /> &lt;span class=&quot;plainlinks&quot;&gt;[{{filepath:CFD12_SST_Ahmed_35_BL_x=-83.dat}} -83]&lt;/span&gt;,<br /> &lt;span class=&quot;plainlinks&quot;&gt;[{{filepath:CFD12_SST_Ahmed_35_BL_x=-63.dat}} -63]&lt;/span&gt;,<br /> &lt;span class=&quot;plainlinks&quot;&gt;[{{filepath:CFD12_SST_Ahmed_35_BL_x=-43.dat}} -43]&lt;/span&gt;,<br /> &lt;span class=&quot;plainlinks&quot;&gt;[{{filepath:CFD12_SST_Ahmed_35_BL_x=-23.dat}} -23]&lt;/span&gt;,<br /> &lt;span class=&quot;plainlinks&quot;&gt;[{{filepath:CFD12_SST_Ahmed_35_BL_x=-3.dat}} -3]&lt;/span&gt;<br /> <br /> Pressure coefficients on the rear of the body:<br /> &lt;span class=&quot;plainlinks&quot;&gt;[{{filepath:CFD12_SST_Ahmed_35_Cp.dat}} Cp]&lt;/span&gt;<br /> <br /> <br /> <br /> '''EASM model'''<br /> <br /> 25° slant angle:<br /> <br /> planes:<br /> &lt;span class=&quot;plainlinks&quot;&gt;[{{filepath:CFD12_EASM_Ahmed_25_y=0.dat}} y=0]&lt;/span&gt;;<br /> &lt;span class=&quot;plainlinks&quot;&gt;[{{filepath:CFD12_EASM_Ahmed_25_y=100.dat}} y=100]&lt;/span&gt;; <br /> &lt;span class=&quot;plainlinks&quot;&gt;[{{filepath:CFD12_EASM_Ahmed_25_y=180.dat}} y=180]&lt;/span&gt;;<br /> <br /> &lt;span class=&quot;plainlinks&quot;&gt;[{{filepath:CFD12_EASM_Ahmed_25_y=195.dat}} y=195]&lt;/span&gt;;<br /> &lt;span class=&quot;plainlinks&quot;&gt;[{{filepath:CFD12_EASM_Ahmed_25_z=360.dat}} z=360]&lt;/span&gt;<br /> <br /> &lt;span class=&quot;plainlinks&quot;&gt;[{{filepath:CFD12_EASM_Ahmed_25_x=-794.dat}} x=-794]&lt;/span&gt;;<br /> &lt;span class=&quot;plainlinks&quot;&gt;[{{filepath:CFD12_EASM_Ahmed_25_x=-178.dat}} x=-178]&lt;/span&gt;;<br /> &lt;span class=&quot;plainlinks&quot;&gt;[{{filepath:CFD12_EASM_Ahmed_25_x=-138.dat}} x=-138]&lt;/span&gt;;<br /> &lt;span class=&quot;plainlinks&quot;&gt;[{{filepath:CFD12_EASM_Ahmed_25_x=-88.dat}} x=-88]&lt;/span&gt;;<br /> &lt;span class=&quot;plainlinks&quot;&gt;[{{filepath:CFD12_EASM_Ahmed_25_x=-38.dat}} x=-38]&lt;/span&gt;;<br /> &lt;span class=&quot;plainlinks&quot;&gt;[{{filepath:CFD12_EASM_Ahmed_25_x=0.dat}} x=0]&lt;/span&gt;;<br /> &lt;span class=&quot;plainlinks&quot;&gt;[{{filepath:CFD12_EASM_Ahmed_25_x=80.dat}} x=80]&lt;/span&gt;;<br /> &lt;span class=&quot;plainlinks&quot;&gt;[{{filepath:CFD12_EASM_Ahmed_25_x=200.dat}} x=200]&lt;/span&gt;;<br /> &lt;span class=&quot;plainlinks&quot;&gt;[{{filepath:CFD12_EASM_Ahmed_25_x=500.dat}} x=500]&lt;/span&gt;<br /> <br /> profiles in the boundary layer:<br /> &lt;span class=&quot;plainlinks&quot;&gt;[{{filepath:CFD12_EASM_Ahmed_25_BL_x=-243.dat}} x=-243]&lt;/span&gt;,<br /> &lt;span class=&quot;plainlinks&quot;&gt;[{{filepath:CFD12_EASM_Ahmed_25_BL_x=-223.dat}} -223]&lt;/span&gt;,<br /> &lt;span class=&quot;plainlinks&quot;&gt;[{{filepath:CFD12_EASM_Ahmed_25_BL_x=-203.dat}} -203]&lt;/span&gt;,<br /> &lt;span class=&quot;plainlinks&quot;&gt;[{{filepath:CFD12_EASM_Ahmed_25_BL_x=-183.dat}} -183]&lt;/span&gt;,<br /> &lt;span class=&quot;plainlinks&quot;&gt;[{{filepath:CFD12_EASM_Ahmed_25_BL_x=-163.dat}} -163]&lt;/span&gt;,<br /> &lt;span class=&quot;plainlinks&quot;&gt;[{{filepath:CFD12_EASM_Ahmed_25_BL_x=-143.dat}} -143]&lt;/span&gt;,<br /> &lt;span class=&quot;plainlinks&quot;&gt;[{{filepath:CFD12_EASM_Ahmed_25_BL_x=-123.dat}} -123]&lt;/span&gt;,<br /> &lt;span class=&quot;plainlinks&quot;&gt;[{{filepath:CFD12_EASM_Ahmed_25_BL_x=-103.dat}} -103]&lt;/span&gt;,<br /> &lt;span class=&quot;plainlinks&quot;&gt;[{{filepath:CFD12_EASM_Ahmed_25_BL_x=-83.dat}} -83]&lt;/span&gt;,<br /> &lt;span class=&quot;plainlinks&quot;&gt;[{{filepath:CFD12_EASM_Ahmed_25_BL_x=-63.dat}} -63]&lt;/span&gt;,<br /> &lt;span class=&quot;plainlinks&quot;&gt;[{{filepath:CFD12_EASM_Ahmed_25_BL_x=-43.dat}} -43]&lt;/span&gt;,<br /> &lt;span class=&quot;plainlinks&quot;&gt;[{{filepath:CFD12_EASM_Ahmed_25_BL_x=-23.dat}} -23]&lt;/span&gt;,<br /> &lt;span class=&quot;plainlinks&quot;&gt;[{{filepath:CFD12_EASM_Ahmed_25_BL_x=-3.dat}} -3]&lt;/span&gt;<br /> <br /> Pressure coefficients on the rear of the body:<br /> &lt;span class=&quot;plainlinks&quot;&gt;[{{filepath:CFD12_EASM_Ahmed_25_Cp.dat}} Cp]&lt;/span&gt;<br /> <br /> <br /> 35° slant angle:<br /> <br /> planes:<br /> &lt;span class=&quot;plainlinks&quot;&gt;[{{filepath:CFD12_EASM_Ahmed_35_y=0.dat}} y=0]&lt;/span&gt;;<br /> &lt;span class=&quot;plainlinks&quot;&gt;[{{filepath:CFD12_EASM_Ahmed_35_y=100.dat}} y=100]&lt;/span&gt;; <br /> &lt;span class=&quot;plainlinks&quot;&gt;[{{filepath:CFD12_EASM_Ahmed_35_y=180.dat}} y=180]&lt;/span&gt;;<br /> <br /> &lt;span class=&quot;plainlinks&quot;&gt;[{{filepath:CFD12_EASM_Ahmed_35_y=195.dat}} y=195]&lt;/span&gt;;<br /> &lt;span class=&quot;plainlinks&quot;&gt;[{{filepath:CFD12_EASM_Ahmed_35_z=360.dat}} z=360]&lt;/span&gt;<br /> <br /> &lt;span class=&quot;plainlinks&quot;&gt;[{{filepath:CFD12_EASM_Ahmed_35_x=-794.dat}} x=-794]&lt;/span&gt;;<br /> &lt;span class=&quot;plainlinks&quot;&gt;[{{filepath:CFD12_EASM_Ahmed_35_x=-178.dat}} x=-178]&lt;/span&gt;;<br /> &lt;span class=&quot;plainlinks&quot;&gt;[{{filepath:CFD12_EASM_Ahmed_35_x=-138.dat}} x=-138]&lt;/span&gt;;<br /> &lt;span class=&quot;plainlinks&quot;&gt;[{{filepath:CFD12_EASM_Ahmed_35_x=-88.dat}} x=-88]&lt;/span&gt;;<br /> &lt;span class=&quot;plainlinks&quot;&gt;[{{filepath:CFD12_EASM_Ahmed_35_x=-38.dat}} x=-38]&lt;/span&gt;;<br /> &lt;span class=&quot;plainlinks&quot;&gt;[{{filepath:CFD12_EASM_Ahmed_35_x=0.dat}} x=0]&lt;/span&gt;;<br /> &lt;span class=&quot;plainlinks&quot;&gt;[{{filepath:CFD12_EASM_Ahmed_35_x=80.dat}} x=80]&lt;/span&gt;;<br /> &lt;span class=&quot;plainlinks&quot;&gt;[{{filepath:CFD12_EASM_Ahmed_35_x=200.dat}} x=200]&lt;/span&gt;;<br /> &lt;span class=&quot;plainlinks&quot;&gt;[{{filepath:CFD12_EASM_Ahmed_35_x=500.dat}} x=500]&lt;/span&gt;<br /> <br /> profiles in the boundary layer:<br /> &lt;span class=&quot;plainlinks&quot;&gt;[{{filepath:CFD12_EASM_Ahmed_35_BL_x=-243.dat}} x=-243]&lt;/span&gt;,<br /> &lt;span class=&quot;plainlinks&quot;&gt;[{{filepath:CFD12_EASM_Ahmed_35_BL_x=-223.dat}} -223]&lt;/span&gt;,<br /> &lt;span class=&quot;plainlinks&quot;&gt;[{{filepath:CFD12_EASM_Ahmed_35_BL_x=-203.dat}} -203]&lt;/span&gt;,<br /> &lt;span class=&quot;plainlinks&quot;&gt;[{{filepath:CFD12_EASM_Ahmed_35_BL_x=-183.dat}} -183]&lt;/span&gt;,<br /> &lt;span class=&quot;plainlinks&quot;&gt;[{{filepath:CFD12_EASM_Ahmed_35_BL_x=-163.dat}} -163]&lt;/span&gt;,<br /> &lt;span class=&quot;plainlinks&quot;&gt;[{{filepath:CFD12_EASM_Ahmed_35_BL_x=-143.dat}} -143]&lt;/span&gt;,<br /> &lt;span class=&quot;plainlinks&quot;&gt;[{{filepath:CFD12_EASM_Ahmed_35_BL_x=-123.dat}} -123]&lt;/span&gt;,<br /> &lt;span class=&quot;plainlinks&quot;&gt;[{{filepath:CFD12_EASM_Ahmed_35_BL_x=-103.dat}} -103]&lt;/span&gt;,<br /> &lt;span class=&quot;plainlinks&quot;&gt;[{{filepath:CFD12_EASM_Ahmed_35_BL_x=-83.dat}} -83]&lt;/span&gt;,<br /> &lt;span class=&quot;plainlinks&quot;&gt;[{{filepath:CFD12_EASM_Ahmed_35_BL_x=-63.dat}} -63]&lt;/span&gt;,<br /> &lt;span class=&quot;plainlinks&quot;&gt;[{{filepath:CFD12_EASM_Ahmed_35_BL_x=-43.dat}} -43]&lt;/span&gt;,<br /> &lt;span class=&quot;plainlinks&quot;&gt;[{{filepath:CFD12_EASM_Ahmed_35_BL_x=-23.dat}} -23]&lt;/span&gt;,<br /> &lt;span class=&quot;plainlinks&quot;&gt;[{{filepath:CFD12_EASM_Ahmed_35_BL_x=-3.dat}} -3]&lt;/span&gt;<br /> <br /> Pressure coefficients on the rear of the body:<br /> &lt;span class=&quot;plainlinks&quot;&gt;[{{filepath:CFD12_EASM_Ahmed_35_Cp.dat}} Cp]&lt;/span&gt;<br /> <br /> =='''References CFD12'''==<br /> <br /> C.L. Rumsey, Application of CFL3D to case 9.4 (Ahmed Body), in: R. Manceau, J.-P. Bonnet, editors, 10th ERCOFTAC (SIG-15)/IAHR/QNET-CFD Workshop on Refined Turbulence Modelling, Oct. 10-11, 2002, Laboratoire d’études aérodynamiques, UMR CNRS 6609, Université de Poitiers, France.<br /> <br /> <br /> =='''Simulation Case CFD13'''==<br /> <br /> ==='''Solution strategy CFD13'''===<br /> <br /> RANS modelling.<br /> <br /> In-house code STREAM, which is a finite volume solver which uses a structured, non-orthogonal curvilinear, multi block grid and a fully collocated arrangement. The SIMPLE pressure correction method and Rie &amp; Chow interpolation are used to prevent unrealistic pressure fluctuations. The convection terms are discretized using an upwind scheme or a TVD scheme based on the third-order QUICK scheme<br /> <br /> Reynolds number: 2.78x106 (see EXP2). Steady state computation.<br /> <br /> Slant angle: 25°.<br /> <br /> ==='''Computational Domain CFD13'''===<br /> <br /> Symmetry is used to compute half the domain. No stilts included.<br /> <br /> Domain: [-3L;6L]x[0;0.9L]x[0;1.15L]<br /> <br /> Mesh : 1.3x106 cells<br /> <br /> Approximate value of y+ on solid surfaces : 1<br /> <br /> ==='''Boundary Conditions CFD13'''===<br /> <br /> Inlet: no details<br /> <br /> Solid boundaries: no-slip walls<br /> <br /> Other boundaries: symmetry<br /> <br /> ===''''Application of Physical Models CFD13'''===<br /> <br /> All are low-Reynolds number models<br /> <br /> - Linear k-ε model (Launder-Sharma)<br /> <br /> - Linear k-ω model (Wilcox)<br /> <br /> - Cubic k-ε model (Apsley, Leschziner)<br /> <br /> - Quadratic k-ω model (Abe, Jang, Leschziner)<br /> <br /> - Quadratic k-ε model (Abe, Jang, Leschziner)<br /> <br /> - SSG + Chen (Abe, Jang, Leschziner)<br /> <br /> ==='''Numerical Accuracy CFD13'''===<br /> <br /> No details<br /> <br /> ==='''CFD Results CFD13'''===<br /> <br /> Cp contours on the slant part, velocity profiles in the boundary layer over the slant part, vectors plots in 13 planes (see EXP2).<br /> <br /> =='''References CFD13'''==<br /> '''Y.J. Jang, M. Leschziner, Contribution of Imperial College to Test Case 9.4: Flow around a simplified car body, In: R. Manceau, J.-P. Bonnet, editors, '''''10th ERCOFTAC (SIG-15)/IAHR/QNET-CFD Workshop on Refined Turbulence Modelling, Oct. 10-11, 2002, Laboratoire d’études aérodynamiques, UMR CNRS 6609, Université de Poitiers, France.'''''<br /> <br /> <br /> =='''Simulation Case CFD14'''==<br /> <br /> ==='''Solution strategy CFD14'''===<br /> <br /> RANS modelling.<br /> <br /> In-house code ISIS, based on unstructured finite volume discretization.<br /> <br /> Reynolds number: 2.78x106 (see EXP2). Steady state computation.<br /> <br /> Slant angle: 25° and 35°.<br /> <br /> ==='''Computational Domain CFD14'''===<br /> <br /> Symmetry is used to compute half the domain.<br /> <br /> Domain: [-4L;5L]x[0;0.9L]x[0;1.35L]<br /> <br /> Mesh : 3.8x106 cells<br /> <br /> Approximate value of y+ on solid surfaces: 0.5<br /> <br /> ==='''Boundary Conditions CFD14'''===<br /> <br /> Solid boundaries: no slip wall<br /> <br /> Symmetry plane: symmetry<br /> <br /> Other boundaries: no details<br /> <br /> ==='''Application of Physical Models CFD14'''===<br /> <br /> SST model<br /> <br /> ==='''Numerical Accuracy CFD14'''===<br /> <br /> No details<br /> <br /> ==='''CFD Results CFD14'''===<br /> <br /> Velocity profiles in the boundary layer over the slant part, streamlines, turbulent energy contours.<br /> <br /> =='''References CFD14'''==<br /> <br /> E. Guilmineau, Numerical simulation of flow around a simplified car body, Proc. ASME JSME Joint Fluids Engineering Conference, July 6-10, 2003, Honolulu, Hawaii, USA<br /> <br /> <br /> =='''Simulation Case CFD15'''==<br /> <br /> ==='''Solution strategy CFD15'''===<br /> <br /> RANS modelling.<br /> <br /> Commercial StarCD code, based on unstructured finite volume discretization.<br /> <br /> Reynolds number: 2.78x106 (see EXP2). Steady state computation.<br /> <br /> Slant angle: 25°.<br /> <br /> ==='''Computational Domain CFD15'''===<br /> <br /> Symmetry is used to compute half the domain. No stilts included. The ground plate starts 2L upstream of the body in order to reproduce the experimental boundary layer.<br /> <br /> Domain: [-5.75L;5.75L]x[0;L]x[0;1.35L]<br /> <br /> Mesh : 1.6x106 cells<br /> <br /> Approximate value of y+ on solid surfaces : &lt; 3<br /> <br /> ==='''Boundary Conditions CFD15'''===<br /> <br /> Inlet: turbulence level 0.1%, nt/n=10.<br /> <br /> Outlet: convective outlet.<br /> <br /> Solid boundaries: no-slip walls<br /> <br /> Symmetry plane: symmetry<br /> <br /> Other boundaries: symmetry<br /> <br /> ==='''Application of Physical Models CFD15'''===<br /> <br /> Rescaled V2F model (Manceau, Carlson, Gatski)<br /> <br /> ==='''Numerical Accuracy CFD15'''===<br /> <br /> No details.<br /> <br /> ==='''CFD Results CFD15'''===<br /> <br /> Vector plots.<br /> <br /> =='''References CFD15'''==<br /> <br /> R. Manceau, Computation of the flow around a simplified car using the rescaled v2f model, ''Proc. ASME JSME Joint Fluids Engineering Conference, July 6-10, 2003, Honolulu, Hawaii, USA''<br /> <br /> <br /> {| align=&quot;center&quot; width=&quot;700&quot; border=&quot;1&quot;<br /> |+ align=&quot;bottom&quot; | Table CFD-A Summary Description of CFD1 - CFD15 Test Cases<br /> ! NAME<br /> ! Re x 10&lt;sup&gt;-6&lt;/sup&gt;<br /> ! width=&quot;90&quot; | Slant angle (degrees)<br /> ! colspan=&quot;2&quot; | [[DOAPs#SPs:_Simulated_Parameters|SPs]]<br /> |-<br /> |<br /> |<br /> |<br /> ! width=&quot;80&quot; | Detailed Data<br /> ! [[DOAPs#DOAPs:_Design_or_Assessment_Parameters|DOAP]]<br /> |-<br /> ! align=&quot;left&quot; | CFD1<br /> | align=&quot;center&quot; | 4.29<br /> | align=&quot;center&quot; | 0, 10, 12, 20, 25, 30, 40, 50<br /> | align=&quot;center&quot; | Pressure&amp;nbsp;Tomographies<br /> | align=&quot;center&quot; | C&lt;sub&gt;d&lt;/sub&gt;, Streamlines, Friction&amp;nbsp;Lines<br /> |-<br /> ! align=&quot;left&quot; | CFD2<br /> | align=&quot;center&quot; | 4.29<br /> | align=&quot;center&quot; | 30<br /> | align=&quot;center&quot; | Effective&amp;nbsp;Viscosity<br /> | align=&quot;center&quot; | C&lt;sub&gt;D&lt;/sub&gt;, Velocities<br /> |-<br /> ! align=&quot;left&quot; | CFD3<br /> | align=&quot;center&quot; | 4.29<br /> | align=&quot;center&quot; | 28<br /> | align=&quot;center&quot; | Pressure&amp;nbsp;Coefficient, Q-criterion&amp;nbsp;Contours<br /> | align=&quot;center&quot; | C&lt;sub&gt;d&lt;/sub&gt;, Velocities, Vorticity&amp;nbsp;Contours<br /> |-<br /> ! align=&quot;left&quot; | CFD4<br /> | align=&quot;center&quot; | 2.78<br /> | align=&quot;center&quot; | 25, 35<br /> | align=&quot;center&quot; | C&lt;sub&gt;P&lt;/sub&gt;<br /> | align=&quot;center&quot; | Velocity&amp;nbsp;Profiles<br /> |-<br /> ! align=&quot;left&quot; | CFD5<br /> | align=&quot;center&quot; | 2.78<br /> | align=&quot;center&quot; | 25, 35<br /> | align=&quot;center&quot; | C&lt;sub&gt;P&lt;/sub&gt;, Turbulent&amp;nbsp;Energy&amp;nbsp;Contours<br /> | align=&quot;center&quot; | Velocity&amp;nbsp;Profiles, Vector&amp;nbsp;Plots, Streamlines<br /> |-<br /> ! align=&quot;left&quot; | CFD6<br /> | align=&quot;center&quot; | 2.78<br /> | align=&quot;center&quot; | 25<br /> | align=&quot;center&quot; | C&lt;sub&gt;P&lt;/sub&gt;<br /> | align=&quot;center&quot; | Velocity&amp;nbsp;Profiles<br /> |-<br /> ! align=&quot;left&quot; | CFD7<br /> | align=&quot;center&quot; | 2.78<br /> | align=&quot;center&quot; | 35<br /> | align=&quot;center&quot; | C&lt;sub&gt;P&lt;/sub&gt;<br /> | align=&quot;center&quot; | Velocity&amp;nbsp;Profiles, Vector&amp;nbsp;Plots<br /> |-<br /> ! align=&quot;left&quot; | CFD8<br /> | align=&quot;center&quot; | 2.78<br /> | align=&quot;center&quot; | 25, 35<br /> | align=&quot;center&quot; | C&lt;sub&gt;P&lt;/sub&gt;<br /> | align=&quot;center&quot; | Velocity&amp;nbsp;Profiles, Vector&amp;nbsp;Plots<br /> |-<br /> ! align=&quot;left&quot; | CFD9<br /> | align=&quot;center&quot; | 2.78<br /> | align=&quot;center&quot; | 25, 35<br /> | align=&quot;center&quot; | C&lt;sub&gt;P&lt;/sub&gt;<br /> | align=&quot;center&quot; | Velocity&amp;nbsp;Profiles, Vector&amp;nbsp;Plots<br /> |-<br /> ! align=&quot;left&quot; | CFD10<br /> | align=&quot;center&quot; | 2.78<br /> | align=&quot;center&quot; | 25<br /> | align=&quot;center&quot; | C&lt;sub&gt;P&lt;/sub&gt;<br /> | align=&quot;center&quot; | Velocity&amp;nbsp;Profiles, Vector&amp;nbsp;Plots<br /> |-<br /> ! align=&quot;left&quot; | CFD11<br /> | align=&quot;center&quot; | 2.78<br /> | align=&quot;center&quot; | 35<br /> | align=&quot;center&quot; | C&lt;sub&gt;P&lt;/sub&gt;<br /> | align=&quot;center&quot; | C&lt;sub&gt;d&lt;/sub&gt;, Velocity&amp;nbsp;Profiles, Vector&amp;nbsp;Plots<br /> |-<br /> ! align=&quot;left&quot; | CFD12<br /> | align=&quot;center&quot; | 2.78<br /> | align=&quot;center&quot; | 25, 35<br /> | align=&quot;center&quot; | C&lt;sub&gt;P&lt;/sub&gt;<br /> | align=&quot;center&quot; | Velocity&amp;nbsp;Profiles, Vector&amp;nbsp;Plots<br /> |-<br /> ! align=&quot;left&quot; | CFD13<br /> | align=&quot;center&quot; | 2.78<br /> | align=&quot;center&quot; | 25<br /> | align=&quot;center&quot; | C&lt;sub&gt;P&lt;/sub&gt;<br /> | align=&quot;center&quot; | Velocity&amp;nbsp;Profiles, Vector&amp;nbsp;Plots<br /> |-<br /> ! align=&quot;left&quot; | CFD14<br /> | align=&quot;center&quot; | 2.78<br /> | align=&quot;center&quot; | 25, 35<br /> | align=&quot;center&quot; | Turbulent&amp;nbsp;Energy&amp;nbsp;Contours<br /> | align=&quot;center&quot; | Velocity&amp;nbsp;Profiles, Streamlines<br /> |-<br /> ! align=&quot;left&quot; | CFD15<br /> | align=&quot;center&quot; | 2.78<br /> | align=&quot;center&quot; | 25<br /> |<br /> | align=&quot;center&quot; | Vector&amp;nbsp;Plots<br /> |}<br /> <br /> =='''Simulation Case CFD16 (added in 2024 by F.R. Menter)'''==<br /> <br /> ==='''Solution Strategy CFD16'''===<br /> <br /> Large Eddy Simulation – Several simulations using different wall treatments and different meshes. <br /> <br /> Commercial Fluent and Fluent-GPU codes<br /> <br /> Reynolds number 2.78e6 (EXP2) (also simulations for lower Re=0.72e6)<br /> <br /> Slant angle 25°<br /> <br /> ==='''Computational Domain CFD16'''===<br /> <br /> All geometry included.<br /> <br /> Domain [m] [-3,6] x [-3,3] x [0, 3.5]<br /> <br /> Meshes from 7e6 to 560e6. (given in reference)<br /> <br /> Y+ values varying for different meshes (wall-resolved to wall function meshes)<br /> <br /> ==='''Boundary Conditions CFD16'''===<br /> <br /> Inlet – Velocity constant<br /> <br /> Bottom wind tunnel wall: non-slip<br /> <br /> Other wind tunnel walls: Slip walls<br /> <br /> Outlet: Pressure outlet<br /> <br /> ==='''Application of Physical Models CFD16'''===<br /> <br /> (described in Fluent Manual A.F.U. R-22.1, 2022)<br /> <br /> WALE model<br /> <br /> Wall-Resolved LES<br /> <br /> Wall-Function LES<br /> <br /> ==='''Numerical Accuracy CFD16'''===<br /> <br /> 2nd order code<br /> <br /> Wide range of meshes (given in reference)<br /> <br /> ==='''CFD Results CFD16'''===<br /> <br /> Wall shear stress on the roof-center plane, velocity and streamwise fluctuation profiles on the slant, wall streamlines on the slant, turbulent structures around the car body.<br /> <br /> =='''References CFD16'''==<br /> <br /> Menter, F.R., Hüppe, A., Flad, D. et al. Large Eddy Simulations for the Ahmed Car at 25° Slant Angle at Different Reynolds Numbers. Flow Turbulence Combust 112, 321–343 (2024).<br /> <br /> <br /> <br /> <br /> © copyright ERCOFTAC 2004<br /> <br /> ----<br /> <br /> <br /> ''Contributors: Remi Manceau; Jean-Paul Bonnet - Université de Poitiers. &amp;mdash; Update (2024) F.R.Menter, ANSYS Germany '', <br /> <br /> Site Design and Implementation:[[Atkins]] and [[UniS]]<br /> <br /> {{AC|front=AC 1-05|description=Description_AC1-05|testdata=Test Data_AC1-05|cfdsimulations=CFD Simulations_AC1-05|evaluation=Evaluation_AC1-05|qualityreview=Quality Review_AC1-05|bestpractice=Best Practice Advice_AC1-05|relatedUFRs=Related UFRs_AC1-05}}</div> Mike https://kbwiki.ercoftac.org/w/index.php?title=Description_AC1-05&diff=45221 Description AC1-05 2024-03-04T10:35:21Z <p>Mike: </p> <hr /> <div>{{AC|front=AC 1-05|description=Description_AC1-05|testdata=Test Data_AC1-05|cfdsimulations=CFD Simulations_AC1-05|evaluation=Evaluation_AC1-05|qualityreview=Quality Review_AC1-05|bestpractice=Best Practice Advice_AC1-05|relatedUFRs=Related UFRs_AC1-05}}<br /> <br /> ='''Ahmed body'''=<br /> <br /> '''Application Challenge 1-05''' © copyright ERCOFTAC 2004<br /> <br /> <br /> <br /> =='''Introduction'''==<br /> <br /> A basic ground vehicle type of bluff body is investigated. The body consists of three parts : a fore-body, a mid section and a rear end.<br /> <br /> Two experiments are available:<br /> <br /> The first one (Exp1) was performed at DLR-Göttingen in a wind tunnel at Reynolds number 4.29 million (60 m/s), based on the model length. The model is mounted on a ground plate, in order to reproduce the ground effect. The angle of the rear end slope is adjustable, between 0 and 40° with a 5° step. More details are available for angles of 5°, 12.5° and 30°. Pressure is measured by about 210 pressure probes on the fore-body, 83 in the mid section and 450 on rear ends. Friction lines <br /> visualizations are also available. Moreover, detailed wake surveys are performed with 10 hole probes and drag measurements are provided.<br /> <br /> <br /> <br /> The second, more recent experiment (Exp2) was provided by Erlangen LSTM within the MOVA “Models for Vehicle Aerodynamics” European project (TU Delft, Univ. of Manchester (UMIST), LSTM, Electricité de France, AVL List, PSA Peugeot-Citroën). The same model is used as in the previous study, but the Reynolds number is reduced to 2.78 million (40m/s), and the study is focused on slant angles close to the drag crisis, 25° and 35°. Two-component hot wire measurements were performed in the boundary layer above the slant part and LDA measurements in 13 different planes. Mean values and turbulence statistics (second and third moments) are provided. Pressure measurements were performed on the rear part of the model (435 pressure probes). Oil/soot friction lines visualizations are also provided.<br /> <br /> The Ahmed body was one of the test cases of the 9th and 10th ERCOFTAC-IAHR Workshop on Refined Turbulence Modeling held in Darmstad, Germany (2001) and Poitiers, France (2002) respectively. These workshops were organized under the auspices of the Special Interest Group 15 on Turbulence Modeling of ERCOFTAC. The proceedings of the 10th ERCOFTAC-IAHR Workshop can be found at:<br /> <br /> [https://hal.science/hal-03037095 https://hal.science/hal-03037095]<br /> <br /> and this test case at:<br /> <br /> [https://kbwiki-images.s3.amazonaws.com/c/ce/Ahmed.florian.menter.pdf Test Case 9.4]<br /> <br /> CFD results were obtained by 15 different teams, ranging from simple RANS models (standard k-epsilon model with wall functions) to more elaborate RANS models and even LES.<br /> <br /> After the ERCOFTAC workshops in the early 2000’s, CFD simulations were mainly carried out with LES and hybrid RANS-LES methods. An update on these simulations was added in 2024 to this document by F.R. Menter including LES results for the 25° slant angle case from Menter et al (2024) - Reference see Abstract.<br /> <br /> =='''Relevance to Industrial Sector'''==<br /> <br /> The basic shape of the so-called « Ahmed body » contains important features of real road vehicles : a main body, followed by a fully separated region. Prediction of separated flows is one of the more difficult task of CFD. The parametric variation of the angle of the rear part allows the study of various configuration relevant to real car characteristics, from massively separated, “simple” wakes, to very complex, 3D wake structures. The reproduction of this complex, 3D wake is very challenging for CFD, as well as the transition from one behaviour to another. The data base contains also drag results that are essential to predict for practical purposes, and are closely related to the structure of the wake.<br /> <br /> The second set of experiments provides very detailed results, including turbulent quantities that are useful for a detailed analysis of turbulence models.<br /> <br /> <br /> =='''Design or Assessment Parameters'''==<br /> <br /> The first [[DOAP]] is the drag coefficient, and in particular its variations with the slant angle.<br /> <br /> A second [[DOAP]] is the topology of the flow, which is crucial for the correct reproduction of the drag coefficient. Comparisons between computations and experiments in the provided planes and in the boundary layer will be useful, as well as friction lines visualizations on the slant part and the vertical base.<br /> <br /> <br /> =='''Flow Domain Geometry'''==<br /> <br /> <br /> {|align=&quot;center&quot;<br /> |[[Image:Image22.gif]]<br /> |-<br /> |''Figure 1:'' Geometry of the Ahmed body <br /> |}<br /> <br /> <br /> <br /> The model is described on Figure 1. The geometry of the fore-body is available in<br /> &lt;span class=&quot;plainlinks&quot;&gt;[{{filepath:Ahmed_Front_Geo.dat}} Ahmed_Front_Geo.dat]&lt;/span&gt;.<br /> <br /> X, Y and Z are the streamwise, spanwise and ground-normal directions, respectively. The origin of the axes is the point at the intersection between the vertical base (X=0), the symmetry plane (Y=0) and the ground plate (Z=0).<br /> <br /> Overall length: 1.044 m. Width 0.389 m, Height 0.288 m.<br /> <br /> The forebody is 0.182 m long, the center of the curvature being placed 100 mm from the front and upper/lower/lateral surfaces. The central (constant section area) is 0.640 m long.<br /> <br /> All rear ends have the same slant part length Ls= 222mm. The edges are sharp.<br /> <br /> The model is placed in a 3/4-open test section (only the floor is present). No indication on the homogeneity of the flow is given.<br /> <br /> Special attention should be given on the presence of a ground plate between the tunnel floor and the body. This plate is used for preventing wind tunnel boundary layer parasitic effects on the model. The model lies 50 mm above it and is placed on stilts of 30 mm diameter.<br /> <br /> =='''Flow Physics and Fluid Dynamics Data'''==<br /> <br /> The flow has no special characteristics. Air at ambiant conditions is used. The model is supposed to be smooth.<br /> <br /> © copyright ERCOFTAC 2004<br /> <br /> ----<br /> <br /> <br /> ''Contributors: Remi Manceau; Jean-Paul Bonnet - Université de Poitiers. &amp;mdash; Update (2024) F.R.Menter, ANSYS Germany '', <br /> <br /> <br /> {{AC|front=AC 1-05|description=Description_AC1-05|testdata=Test Data_AC1-05|cfdsimulations=CFD Simulations_AC1-05|evaluation=Evaluation_AC1-05|qualityreview=Quality Review_AC1-05|bestpractice=Best Practice Advice_AC1-05|relatedUFRs=Related UFRs_AC1-05}}</div> Mike https://kbwiki.ercoftac.org/w/index.php?title=News&diff=45217 News 2024-02-14T11:21:05Z <p>Mike: /* February 2023: Update to AC 1-05 Ahmed body flow */</p> <hr /> <div>__NOTOC__<br /> &lt;div id=&quot;contents&quot;&gt;&lt;/div&gt;<br /> <br /> ==February 2024: Update to AC 1-05 Ahmed body flow==<br /> AC 1-05 [[AC_1-05|Ahmed body flow]] has been updated with new LES results added.<br /> <br /> ==August 2023: New EXP case added to wiki==<br /> A new EXP case (EXP1-4) [[EXP_1-4|Axisymmetric drop impact dynamics on a wall film of the same liquid]] is now available in the [[EXP_Index| EXP]] section.<br /> <br /> ==August 2023: New EXP case added to wiki==<br /> A new EXP case (EXP1-1) [[EXP_1-1|Pressure-swirl spray in a low-turbulence cross-flow]] is now available in the [[EXP_Index| EXP]] section.<br /> <br /> ==August 2023: First EXP case added to wiki==<br /> The first EXP case has now been added to the wiki. (EXP1-2) [[EXP_1-2|Pollutant transport between a street canyon and a 3D urban array as a function of wind direction and roof height non-uniformity]] is now available in the [[EXP_Index| EXP]] section.<br /> <br /> ==February 2023: New DNS case added to wiki==<br /> A new DNS case (DNS1-6) [[DNS_1-6|3D wing-body junction]] is now available in the [[DNS_Index| DNS]] section.<br /> <br /> ==February 2023: New DNS case added to wiki==<br /> A new DNS case (DNS1-5) [[DNS_1-5|HiFi-TURB-DLR rounded step]] is now available in the [[DNS_Index| DNS]] section.<br /> <br /> ==February 2023: New UFR added to wiki==<br /> A new UFR (UFR3-36) [[UFR_3-36|HiFi-TURB-DLR rounded step]] has been added to the Semi-confined flows section.<br /> <br /> ==January 2023: New AC added to wiki==<br /> A new AC (AC7-03) [[AC7-03|Flow in a Ventricular Assist Device - Pump Performance &amp; Blood Damage Prediction]] has been added to the Biomedical Flows section.<br /> <br /> ==January 2023: New DNS case added to wiki==<br /> A new DNS case (DNS1-3) [[DNS_1-3|Flow in a 3D diffuser]] is now available in the [[DNS_Index| DNS]] section.<br /> <br /> ==January 2023: First DNS case added to wiki==<br /> The first DNS case has now be added to the wiki. (DNS1-2) [[DNS_1-2|DNS Channel Flow]] is now available in the [[DNS_Index| DNS]] section.<br /> <br /> ==January 2022: New AC added to wiki==<br /> A new AC (AC7-04) [[AC7-04|A pulsatile 3D flow relevant to thoracic hemodynamics: CFD - 4D Flow MRI comparison]] has been added to the Biomedical Flows section.<br /> <br /> ==November 2020: New UFR added to wiki==<br /> A new UFR (UFR3-35) [[UFR_3-35|Cylinder-wall junction flow]] has been added to the Semi-confined flows section.<br /> <br /> ==June 2020: New AC added to wiki==<br /> A new AC (AC7-02) [[AC7-02|Airflow in the human upper airways]] has been added to the biomedical flows section.<br /> <br /> ==October 2019: New AC added to new wiki section==<br /> A new section &quot;Biomedical Flows&quot; has been added to the wiki, with a new AC (AC7-01)<br /> [[AC7-01|Aerosol deposition in the human upper airways]].<br /> <br /> ==August 2019: New AC added to wiki==<br /> A new AC (AC2-12) [[AC2-12|Turbulent separated inert and reactive flows over a triangular bluff body]] has been added to the combustion section.<br /> <br /> ==February 2019: New AC added to wiki==<br /> A new AC (AC6-15) [[AC6-15|Vortex ropes in draft tube of a laboratory Kaplan hydro turbine at low load]] has been added to the turbomachinery section.<br /> <br /> ==November 2018: New AC added to wiki==<br /> A new AC (AC2-11) [[AC2-11|Delft-Jet-in-Hot-Coflow (DJHC) burner]] has been added to the combustion section.<br /> <br /> ==November 2018: New AC added to wiki==<br /> A new AC (AC2-10) [[AC2-10|Internal combustion engine flows for motored operation]] has been added to the combustion section.<br /> <br /> ==March 2018: New UFR added to wiki==<br /> A new UFR (UFR3-34) [[UFR_3-34|Smooth wall separation and reattachment at high Reynolds numbers]] has been added to the Semi-confined flows section.<br /> <br /> ==March 2018: New UFR added to wiki==<br /> A new UFR (UFR4-20) [[UFR_4-20|Mixing ventilation flow in an enclosure driven by a transitional wall jet]] has been added to the Confined flows section.<br /> <br /> ==July 2017: Old Wiki Switched Off==<br /> The wiki should now be regarded as being out of beta-test and fully usable. The old wiki has been discontinued.<br /> <br /> ==May 2017: New KB Wiki Launched==<br /> The wiki now has all content available to everybody without the need to log in. The distinction between Gold, Silver and Silver-plus articles has been removed.<br /> <br /> This wiki is now hosted on newer hardware with more up-to-date software. It should be regarded as being in Beta-test until the end of May 2017, when the old server will be switched off. If there are any difficulties encountered, the old site can be accessed via the link in green text at the top of each page. Please direct any queries to the administrator at ellacott@ellacott.plus.com.<br /> <br /> ==August 2016: New AC added to wiki==<br /> A new AC (AC6-14) [[AC6-14|Swirling flow in a conical diffuser generated with rotor-stator interaction]] has been added to the Turbomachinery internal flow section in the &quot;Silver Star&quot; category.<br /> <br /> ==April 2016: New UFR added to wiki==<br /> A new UFR (UFR4-19) [[UFR_4-19|Converging-diverging transonic diffuser]] has been added to the Confined flows section in the &quot;Silver Star&quot; category.<br /> <br /> ==April 2016: New UFR added to wiki==<br /> A new UFR (UFR3-33) [[UFR_3-33|Turbulent flow past a wall-mounted hemisphere]] has been added to the Semi-confined flows section in the &quot;Silver Star&quot; category.<br /> <br /> ==December 2015: New UFR added to Wiki==<br /> A new UFR (UFR4-18) [[UFR_4-18|Flow and heat transfer in a pin-fin array]] has been added to the Confined Flows section in the &quot;Silver Star&quot; category.<br /> <br /> ==July 2015: New AC added to Wiki==<br /> A new AC (AC1-09) [[AC1-09|Vortex breakdown above a delta wing with sharp leading edge]] has been added to the External Aerodynamics section in the &quot;Silver Star&quot; category.<br /> <br /> ==June 2014: New UFR added to Wiki==<br /> A new UFR (UFR2-14) [[UFR_2-14|Fluid-structure interaction in turbulent flow past cylinder/plate configuration II]] has been added to the Flows Around Bodies section in the &quot;Silver Star&quot; category.<br /> <br /> ==May 2014: New UFR added to Wiki==<br /> A new UFR (UFR2-15) [[UFR_2-15|Benchmark on the Aerodynamics of a Rectangular 5:1 Cylinder (BARC)]] has been added to the Flows<br /> Around Bodies section in the &quot;Silver&quot; category.<br /> <br /> ==December 2013: New UFR added to Wiki==<br /> A new UFR (UFR2-13) [[UFR_2-13|Fluid-structure interaction in turbulent flow past cylinder/plate configuration I]] has been added to the Flows Around Bodies section in the &quot;Silver Star&quot; category.<br /> <br /> ==November 2013: New UFR added to Wiki==<br /> A new UFR (UFR3-32) [[UFR_3-32|Planar shock-wave boundary-layer interaction]] has been added to the Semi-Confined Flows section in the &quot;Silver Star&quot; category.<br /> ==July 2013: Enhancements to UFR3-30 2D Periodic Hill Flow==<br /> Links to results of and documentation on test calculations performed in the European ATAAC project are now included.<br /> <br /> ==May 2013: Enhancements to UFR4-16 Flow in a 3D diffuser==<br /> Links to results of and documentation on test calculations performed in the European ATAAC project are now included.<br /> <br /> ==March 2013: New AC added to Wiki==<br /> A new AC (AC3-12) [[AC3-12|Particle-laden swirling flow]] has been added to the Chemical, Process, Thermal and Nuclear Safety section in the &quot;Silver Star&quot; category.<br /> <br /> ==November 2012: New UFR added to Wiki==<br /> A new UFR (UFR2-12) [[UFR_2-12|Turbulent Flow Past Two-Body Configurations]] has been added to the Flows Around Bodies section in the &quot;Silver Star&quot; category.<br /> <br /> ==September 2012: New UFR added to Wiki==<br /> A new UFR (UFR4-16) [[UFR_4-16|Flow in a 3D diffuser]] has been added to the Confined Flows section in the &quot;Silver Star&quot; category.<br /> <br /> ==July 2012: New UFR added to Wiki==<br /> A new UFR (UFR3-31) [[UFR_3-31|Flow over curved backward-facing step]] has been added to the Semi-confined Flows section in the &quot;Silver Star&quot; category.<br /> <br /> ==September 2011: New UFR added to Wiki==<br /> A new UFR (UFR2-11) [[UFR_2-11|High Reynolds Number Flow around Airfoil in Deep Stall]] has been added to the Flows Around Bodies section in the &quot;Silver Star&quot; category.<br /> <br /> ==June 2011: New AC added to Wiki==<br /> A new AC (AC2-09) [[Sandia Flame D|&quot;Sandia Flame D&quot;]] has been added to the Combustion section in the &quot;Silver Star&quot; category.<br /> <br /> ==March 2011: New AC added to Wiki==<br /> A new AC (AC2-08) [[Premixed Methane-Air Swirl Burner (TECFLAM)|&quot;Premixed Methane-Air Swirl Burner (TECFLAM)&quot;]] has been added to the Combustion section in the &quot;Silver Star&quot; category.<br /> <br /> ==January 2011: New UFR added to Wiki==<br /> A new UFR (UFR2-10) [[Flow Around Finite-Height Circular Cylinder|&quot;Flow Around Finite-Height Circular Cylinder&quot;]] has been added to the Flows Around Bodies section in the &quot;Silver Star&quot; category.<br /> <br /> ==August 2010: Wiki Upgrade and New Server==<br /> We are now running MediaWiki 1.16.0 on a new Linux-based server.<br /> The opportunity is also being taken to upgrade other software components of the wiki in the interests of improving reliability and maintainability.<br /> <br /> ==July 2010: New UFR added to Wiki==<br /> A new UFR (UFR1-07) [[Abstr:Unsteady near-field plume|&quot;Unsteady near-field plume&quot;]]<br /> has been added to the Free Flows section in the &quot;Silver Star&quot; category.<br /> <br /> ==April 2010: New UFR added to Wiki==<br /> A new UFR (UFR1-06) [[Axisymmetric buoyant far-field plume|&quot;Axisymmetric bouyant far-field plume&quot;]]<br /> has been added to the Free Flows section in the &quot;Silver Star&quot; category.<br /> <br /> ==March 2010: New UFR added to Wiki==<br /> A new UFR (UFR3-30) [[2D Periodic Hill Flow|&quot;2D Periodic Hill Flow&quot;]]<br /> has been added to the Semi-confined Flows section in the &quot;Silver Star&quot; category.<br /> <br /> ==January 2010: Wiki Forums Launched==<br /> A user &lt;span class=&quot;plainlinks&quot;&gt;[http://qnet-ercoftac.cfms.org.uk/31frm46 forum]&lt;/span&gt; associated with this wiki has now been launched.<br /> It is intended that this will be the primary channel for queries, feedback and comment.</div> Mike https://kbwiki.ercoftac.org/w/index.php?title=News&diff=45216 News 2024-02-14T09:53:03Z <p>Mike: </p> <hr /> <div>__NOTOC__<br /> &lt;div id=&quot;contents&quot;&gt;&lt;/div&gt;<br /> <br /> ==February 2023: Update to AC 1-05 Ahmed body flow==<br /> AC 1-05 [[AC_1-05|Ahmed body flow]] has been updated.<br /> <br /> ==August 2023: New EXP case added to wiki==<br /> A new EXP case (EXP1-4) [[EXP_1-4|Axisymmetric drop impact dynamics on a wall film of the same liquid]] is now available in the [[EXP_Index| EXP]] section.<br /> <br /> ==August 2023: New EXP case added to wiki==<br /> A new EXP case (EXP1-1) [[EXP_1-1|Pressure-swirl spray in a low-turbulence cross-flow]] is now available in the [[EXP_Index| EXP]] section.<br /> <br /> ==August 2023: First EXP case added to wiki==<br /> The first EXP case has now been added to the wiki. (EXP1-2) [[EXP_1-2|Pollutant transport between a street canyon and a 3D urban array as a function of wind direction and roof height non-uniformity]] is now available in the [[EXP_Index| EXP]] section.<br /> <br /> ==February 2023: New DNS case added to wiki==<br /> A new DNS case (DNS1-6) [[DNS_1-6|3D wing-body junction]] is now available in the [[DNS_Index| DNS]] section.<br /> <br /> ==February 2023: New DNS case added to wiki==<br /> A new DNS case (DNS1-5) [[DNS_1-5|HiFi-TURB-DLR rounded step]] is now available in the [[DNS_Index| DNS]] section.<br /> <br /> ==February 2023: New UFR added to wiki==<br /> A new UFR (UFR3-36) [[UFR_3-36|HiFi-TURB-DLR rounded step]] has been added to the Semi-confined flows section.<br /> <br /> ==January 2023: New AC added to wiki==<br /> A new AC (AC7-03) [[AC7-03|Flow in a Ventricular Assist Device - Pump Performance &amp; Blood Damage Prediction]] has been added to the Biomedical Flows section.<br /> <br /> ==January 2023: New DNS case added to wiki==<br /> A new DNS case (DNS1-3) [[DNS_1-3|Flow in a 3D diffuser]] is now available in the [[DNS_Index| DNS]] section.<br /> <br /> ==January 2023: First DNS case added to wiki==<br /> The first DNS case has now be added to the wiki. (DNS1-2) [[DNS_1-2|DNS Channel Flow]] is now available in the [[DNS_Index| DNS]] section.<br /> <br /> ==January 2022: New AC added to wiki==<br /> A new AC (AC7-04) [[AC7-04|A pulsatile 3D flow relevant to thoracic hemodynamics: CFD - 4D Flow MRI comparison]] has been added to the Biomedical Flows section.<br /> <br /> ==November 2020: New UFR added to wiki==<br /> A new UFR (UFR3-35) [[UFR_3-35|Cylinder-wall junction flow]] has been added to the Semi-confined flows section.<br /> <br /> ==June 2020: New AC added to wiki==<br /> A new AC (AC7-02) [[AC7-02|Airflow in the human upper airways]] has been added to the biomedical flows section.<br /> <br /> ==October 2019: New AC added to new wiki section==<br /> A new section &quot;Biomedical Flows&quot; has been added to the wiki, with a new AC (AC7-01)<br /> [[AC7-01|Aerosol deposition in the human upper airways]].<br /> <br /> ==August 2019: New AC added to wiki==<br /> A new AC (AC2-12) [[AC2-12|Turbulent separated inert and reactive flows over a triangular bluff body]] has been added to the combustion section.<br /> <br /> ==February 2019: New AC added to wiki==<br /> A new AC (AC6-15) [[AC6-15|Vortex ropes in draft tube of a laboratory Kaplan hydro turbine at low load]] has been added to the turbomachinery section.<br /> <br /> ==November 2018: New AC added to wiki==<br /> A new AC (AC2-11) [[AC2-11|Delft-Jet-in-Hot-Coflow (DJHC) burner]] has been added to the combustion section.<br /> <br /> ==November 2018: New AC added to wiki==<br /> A new AC (AC2-10) [[AC2-10|Internal combustion engine flows for motored operation]] has been added to the combustion section.<br /> <br /> ==March 2018: New UFR added to wiki==<br /> A new UFR (UFR3-34) [[UFR_3-34|Smooth wall separation and reattachment at high Reynolds numbers]] has been added to the Semi-confined flows section.<br /> <br /> ==March 2018: New UFR added to wiki==<br /> A new UFR (UFR4-20) [[UFR_4-20|Mixing ventilation flow in an enclosure driven by a transitional wall jet]] has been added to the Confined flows section.<br /> <br /> ==July 2017: Old Wiki Switched Off==<br /> The wiki should now be regarded as being out of beta-test and fully usable. The old wiki has been discontinued.<br /> <br /> ==May 2017: New KB Wiki Launched==<br /> The wiki now has all content available to everybody without the need to log in. The distinction between Gold, Silver and Silver-plus articles has been removed.<br /> <br /> This wiki is now hosted on newer hardware with more up-to-date software. It should be regarded as being in Beta-test until the end of May 2017, when the old server will be switched off. If there are any difficulties encountered, the old site can be accessed via the link in green text at the top of each page. Please direct any queries to the administrator at ellacott@ellacott.plus.com.<br /> <br /> ==August 2016: New AC added to wiki==<br /> A new AC (AC6-14) [[AC6-14|Swirling flow in a conical diffuser generated with rotor-stator interaction]] has been added to the Turbomachinery internal flow section in the &quot;Silver Star&quot; category.<br /> <br /> ==April 2016: New UFR added to wiki==<br /> A new UFR (UFR4-19) [[UFR_4-19|Converging-diverging transonic diffuser]] has been added to the Confined flows section in the &quot;Silver Star&quot; category.<br /> <br /> ==April 2016: New UFR added to wiki==<br /> A new UFR (UFR3-33) [[UFR_3-33|Turbulent flow past a wall-mounted hemisphere]] has been added to the Semi-confined flows section in the &quot;Silver Star&quot; category.<br /> <br /> ==December 2015: New UFR added to Wiki==<br /> A new UFR (UFR4-18) [[UFR_4-18|Flow and heat transfer in a pin-fin array]] has been added to the Confined Flows section in the &quot;Silver Star&quot; category.<br /> <br /> ==July 2015: New AC added to Wiki==<br /> A new AC (AC1-09) [[AC1-09|Vortex breakdown above a delta wing with sharp leading edge]] has been added to the External Aerodynamics section in the &quot;Silver Star&quot; category.<br /> <br /> ==June 2014: New UFR added to Wiki==<br /> A new UFR (UFR2-14) [[UFR_2-14|Fluid-structure interaction in turbulent flow past cylinder/plate configuration II]] has been added to the Flows Around Bodies section in the &quot;Silver Star&quot; category.<br /> <br /> ==May 2014: New UFR added to Wiki==<br /> A new UFR (UFR2-15) [[UFR_2-15|Benchmark on the Aerodynamics of a Rectangular 5:1 Cylinder (BARC)]] has been added to the Flows<br /> Around Bodies section in the &quot;Silver&quot; category.<br /> <br /> ==December 2013: New UFR added to Wiki==<br /> A new UFR (UFR2-13) [[UFR_2-13|Fluid-structure interaction in turbulent flow past cylinder/plate configuration I]] has been added to the Flows Around Bodies section in the &quot;Silver Star&quot; category.<br /> <br /> ==November 2013: New UFR added to Wiki==<br /> A new UFR (UFR3-32) [[UFR_3-32|Planar shock-wave boundary-layer interaction]] has been added to the Semi-Confined Flows section in the &quot;Silver Star&quot; category.<br /> ==July 2013: Enhancements to UFR3-30 2D Periodic Hill Flow==<br /> Links to results of and documentation on test calculations performed in the European ATAAC project are now included.<br /> <br /> ==May 2013: Enhancements to UFR4-16 Flow in a 3D diffuser==<br /> Links to results of and documentation on test calculations performed in the European ATAAC project are now included.<br /> <br /> ==March 2013: New AC added to Wiki==<br /> A new AC (AC3-12) [[AC3-12|Particle-laden swirling flow]] has been added to the Chemical, Process, Thermal and Nuclear Safety section in the &quot;Silver Star&quot; category.<br /> <br /> ==November 2012: New UFR added to Wiki==<br /> A new UFR (UFR2-12) [[UFR_2-12|Turbulent Flow Past Two-Body Configurations]] has been added to the Flows Around Bodies section in the &quot;Silver Star&quot; category.<br /> <br /> ==September 2012: New UFR added to Wiki==<br /> A new UFR (UFR4-16) [[UFR_4-16|Flow in a 3D diffuser]] has been added to the Confined Flows section in the &quot;Silver Star&quot; category.<br /> <br /> ==July 2012: New UFR added to Wiki==<br /> A new UFR (UFR3-31) [[UFR_3-31|Flow over curved backward-facing step]] has been added to the Semi-confined Flows section in the &quot;Silver Star&quot; category.<br /> <br /> ==September 2011: New UFR added to Wiki==<br /> A new UFR (UFR2-11) [[UFR_2-11|High Reynolds Number Flow around Airfoil in Deep Stall]] has been added to the Flows Around Bodies section in the &quot;Silver Star&quot; category.<br /> <br /> ==June 2011: New AC added to Wiki==<br /> A new AC (AC2-09) [[Sandia Flame D|&quot;Sandia Flame D&quot;]] has been added to the Combustion section in the &quot;Silver Star&quot; category.<br /> <br /> ==March 2011: New AC added to Wiki==<br /> A new AC (AC2-08) [[Premixed Methane-Air Swirl Burner (TECFLAM)|&quot;Premixed Methane-Air Swirl Burner (TECFLAM)&quot;]] has been added to the Combustion section in the &quot;Silver Star&quot; category.<br /> <br /> ==January 2011: New UFR added to Wiki==<br /> A new UFR (UFR2-10) [[Flow Around Finite-Height Circular Cylinder|&quot;Flow Around Finite-Height Circular Cylinder&quot;]] has been added to the Flows Around Bodies section in the &quot;Silver Star&quot; category.<br /> <br /> ==August 2010: Wiki Upgrade and New Server==<br /> We are now running MediaWiki 1.16.0 on a new Linux-based server.<br /> The opportunity is also being taken to upgrade other software components of the wiki in the interests of improving reliability and maintainability.<br /> <br /> ==July 2010: New UFR added to Wiki==<br /> A new UFR (UFR1-07) [[Abstr:Unsteady near-field plume|&quot;Unsteady near-field plume&quot;]]<br /> has been added to the Free Flows section in the &quot;Silver Star&quot; category.<br /> <br /> ==April 2010: New UFR added to Wiki==<br /> A new UFR (UFR1-06) [[Axisymmetric buoyant far-field plume|&quot;Axisymmetric bouyant far-field plume&quot;]]<br /> has been added to the Free Flows section in the &quot;Silver Star&quot; category.<br /> <br /> ==March 2010: New UFR added to Wiki==<br /> A new UFR (UFR3-30) [[2D Periodic Hill Flow|&quot;2D Periodic Hill Flow&quot;]]<br /> has been added to the Semi-confined Flows section in the &quot;Silver Star&quot; category.<br /> <br /> ==January 2010: Wiki Forums Launched==<br /> A user &lt;span class=&quot;plainlinks&quot;&gt;[http://qnet-ercoftac.cfms.org.uk/31frm46 forum]&lt;/span&gt; associated with this wiki has now been launched.<br /> It is intended that this will be the primary channel for queries, feedback and comment.</div> Mike https://kbwiki.ercoftac.org/w/index.php?title=Best_Practice_Advice_AC1-05&diff=45215 Best Practice Advice AC1-05 2024-02-14T09:47:16Z <p>Mike: </p> <hr /> <div>{{AC|front=AC 1-05|description=Description_AC1-05|testdata=Test Data_AC1-05|cfdsimulations=CFD Simulations_AC1-05|evaluation=Evaluation_AC1-05|qualityreview=Quality Review_AC1-05|bestpractice=Best Practice Advice_AC1-05|relatedUFRs=Related UFRs_AC1-05}}<br /> <br /> ='''Ahmed body'''=<br /> <br /> '''Application Challenge 1-05''' © copyright ERCOFTAC 2004<br /> <br /> <br /> <br /> =='''Best Practice Advice for the AC'''==<br /> <br /> ==='''Key Fluid Physics'''===<br /> <br /> ==='''A-Key design or assessment parameters [[DOAP]] :'''===<br /> <br /> <br /> <br /> • The Drag coefficient Cd, and in particular its variations with the slant angle (see figure), is the main global parameter to be predicted.<br /> <br /> [[Image:D34_image2.jpg]] <br /> <br /> <br /> <br /> The topology of the flow is crucial for the correct reproduction of the drag coefficient: in particular, the drag crisis around 25-30° corresponds to a transition of the wake structure from a massively separated, quasi-2D structure to a complex, 3D structure.<br /> <br /> <br /> <br /> <br /> <br /> '''B- Key physics :'''<br /> <br /> <br /> <br /> • The contributions of the different components of the drag have different trends when the slant angle changes (see figure).<br /> <br /> <br /> <br /> <br /> <br /> • The component responsible for the drag crisis is the pressure drag due to the slant part , which jumps from 35% of total drag at 35° to 55% at 25°.<br /> <br /> <br /> <br /> <br /> <br /> • The drag crisis corresponds to a dramatic change is the structure of the wake:<br /> <br /> o In the low-drag configuration, the wake is massively-separated, quasi-toroïdal<br /> <br /> o <br /> [[Image:D34_image4.jpg]]<br /> <br /> <br /> <br /> In the high-drag configuration, the wake has a complex, 3D structure: in the central region of the slant part (close to the symmetry plane) experiments show a small separation bubble, with a reattachement on the slant part. This bubble strongly interacts with the highly energetic corner vortices. Other complex phenomena are present (interaction with the underside flow, with side boundary layers, large-scale flapping in the spanwise direction, etc.), but they are not well understood yet.<br /> <br /> <br /> <br /> <br /> <br /> <br /> <br /> '''C- Comparison of CFD and experiments'''<br /> <br /> <br /> <br /> • '''Low-drag configuration (35°):'''<br /> <br /> o Realistic pressure level and distribution on the slant part and vertical base are predicted, even with standard k-epsilon with wall functions<br /> <br /> o The correct trend of the drag with the slant angle is obtained<br /> <br /> o However, quantitative predictions are not correct: pressure drop and drag are generally underestimated<br /> <br /> <br /> <br /> <br /> <br /> • '''High-drag configuration (25°):'''<br /> <br /> o The wake structure transition is missed by almost all models, whatever the numerical accuracy and the conditions of the computation: pressure drop on the base is highly underestimated. Only LES and low-Re RSM are able to reproduce the complex, 3D wake structure but:<br /> <br /> o LES (CFD9) does not reproduce correctly the boundary layer, because of the use of wall functions<br /> <br /> o Low-Re RSM (CFD13) overpredicts the reattachment length and the independance to numerics is not validated enough to draw definitive conclusions<br /> <br /> <br /> ==='''Application Uncertainties'''===<br /> <br /> • The influence of the stilts on the drag is at least 10% (CFD11), but their influence on the structure of the flow under the body is not known precisely, and this may have a significant influence on the wake of the body, which cannot be evaluated.<br /> <br /> • The experiments were performed in a ¾ open test section. The influence of using a finite computational domain is not known.<br /> <br /> ==='''Computational Domain and Boundary Conditions'''===<br /> <br /> '''Computational domain'''<br /> <br /> • ½ body (symmetry) is sufficient for steady-state computations (RANS). Use the full body for unsteady computations (LES, URANS).<br /> <br /> • CFD11 estimates that the stilts roughly contribute to 10% of the drag. Stilts must be included.<br /> <br /> • Include the ground plate: CFD3 shows that the flow without a ground plate is completely different. The ground plate should start 2L (L=body length) in front of the body to mimic the EXP2 profiles (CFD11, CFD15) (however, the importance of this condition has not been demonstrated).<br /> <br /> • Inlet must be placed before x=-3L. Outlet must be sufficiently far to have no influence on the wake: outlet at x=5L is generally used, but no systematic study have been performed.<br /> <br /> • Side and top boundaries: blockage is estimated to 4% in the experiments. To avoid too much blockage in CFD, the minimal recommended cross-section is 2Lx1.35L (for the full body).<br /> <br /> <br /> <br /> '''Boundary conditions'''<br /> <br /> • Use low turbulence intensity at the inlet and small viscosity ratio (I=0.25% and nt / n=10 estimated by EXP2).<br /> <br /> • CFD11 shows that boundary conditions allowing outflow through the side and top boundaries are preferable to slip walls.<br /> <br /> <br /> ==='''Discretisation and Grid Resolution'''===<br /> <br /> '''Discretisation method'''<br /> <br /> • Convection scheme sensitivity studies (CFD11) and comparaison between different teams using the same model and the same mesh show that for the type of grids described below (“marginal resolution”), the solution is sensitive to the convection scheme. Use 2nd order approximation.<br /> <br /> • Sensitivity to other sources of numerical errors (non-orthogonal cells, interpolations, explicit terms) are suspected: care must be taken to avoid 1st order sources of error.<br /> <br /> • Time marching: second order time marching is also advised for unsteady computations, though it is no supported by clear sensitivity studies.<br /> <br /> <br /> <br /> <br /> <br /> '''Grid resolution'''<br /> <br /> • Meshes used in the CFD studies are very complex and precise specifications cannot be given. A grid sensitivity study is strongly advised, since the predictions are very sensitive to the mesh resolution. However, from sensitivity studies and comparisons between computations from different teams with the same models, the following guidelines can be provided (this are minimal constraints to reach an acceptable level of numerical error for global quantities like Cd, not for more sensitive quantities like velocities in the boundary layer):<br /> <br /> o Surface mesh: at least 15000 cells are necessary, which leads to:<br /> <br /> o Volume mesh: at least 0.5x106 cells for high-Re models (y+&gt;30) and at least 1.5x106 cells for low-Re models (y+=1)<br /> <br /> These guidelines are for ½ the body (double the cell number for the full body).<br /> <br /> <br /> ==='''Physical Modelling'''===<br /> <br /> In the Ahmed body test case, predicting correctly the overall quantities (Cd, wake structure) is already a challenge. Therefore, giving advice for predicting flow details would be irrelevant:<br /> <br /> <br /> <br /> '''BPA for overall quantities'''<br /> <br /> • '''Low-drag configurations'''<br /> <br /> All the turbulence models used in the CFD studies give a correct wake structure and Cd trend when varying the angle for low-drag configurations. However, using low-Re models gives a better boundary layer prediction on the slant part. None of the models give the correct quantitative prediction of the pressure distribution on the slant part and vertical base, and, therefore, of the drag.<br /> <br /> o For qualitative predictions in the low-drag configuration, simple eddy-viscosity models with wall functions are sufficient<br /> <br /> o Quantitative predictions cannot be trusted, whatever the model<br /> <br /> <br /> <br /> • '''High-drag configuration'''<br /> <br /> High Reynolds number models (k-ε, RSM) with wall functions must be avoided, because they generally do not predict separation at all, and always fail predicting correct profiles above the slant part.<br /> <br /> Low-Re eddy-viscosity models predict separation provided they are free from the usual stagnation point anomaly (overprediction of turbulence production, see CFD5 study): this is the case for the k-ω/SST model (CFD6, CFD11, CFD12, CFD13, CFD14), non-linear/algebraic k-ε and k-ω models (CFD12, CFD13) and the rescaled V2F model (CFD15). This is not the case for the linear low-Re k-ε model used in CFD10. However, it must be pointed out again that these models predict massive separation, far from experiments.<br /> <br /> Low-Re Reynolds stress models seems to be able to reproduce (too late) reattachment on the slant part and the qualitatively correct wake structure (CFD13). However, this needs to be confirmed by further studies.<br /> <br /> LES (CFD9) is clearly able to reproduce the correct structure of the wake. However, using resolution down to the viscous sublayer is clearly unaffordable for the time being and the use of wall functions does not allow the correct reproduction of the boundary layer above the slant part.<br /> <br /> <br /> ==='''Recommendations for Future Work'''===<br /> <br /> '''Experiments:'''<br /> <br /> • Quantification of the large-scale unsteadiness and investigation of its role in the drag crisis<br /> <br /> <br /> <br /> '''CFD'''<br /> <br /> • The potential of low-Re RSM models must be further investigated<br /> <br /> • Wall-treatment for LES must be improved (see update below)<br /> <br /> • Since accounting for the near-wall region (low-Re RSM) and the large-scale unsteadiness (LES) have beneficial effects, the potential of accounting for both must be investigated: RANS/LES zonal coupling, RANS/LES hybrid models, Unsteady RANS, … (see update below)<br /> <br /> ==='''Update by F. R. Menter added in 2024'''===<br /> <br /> In the years between the ERCOFTAC workshop and today (2024) it was found that steady-state RANS models are not well suited for high accuracy CFD simulations of external automotive geometries. This is well reflected by the contributions to the [https://autocfd.eng.ox.ac.uk/ AutoCFD workshop], where a number of generic and semi-realistic automotive cases have been computed by numerous groups over the years. Most of the contributions to the workshop involve either hybrid RANS-LES or Wall-Function LES applications. This trend increased by the availability of low-cost GPU-based computing power and the corresponding CFD codes, utilizing this advanced hardware. By-and-large an order of magnitude increase in computer-power is achieved at the same cost relative to CPU based clusters. This allows for the wide-spread application of Scale-Resolving Simulations (SRS) to automotive design. <br /> <br /> Even with this increase in computing power, the routine application of wall-resolved LES is not a practical option for engineering simulations. The most popular SRS methods are therefore global hybrid models like [https://link.springer.com/article/10.1007/s10494-011-9378-4 DDES] or [https://link.springer.com/chapter/10.1007/978-3-319-70031-1_3 SBES]. In these models, the attached boundary layer is covered by the RANS model whereas separated regions are automatically detected by the shielding functions and the models switch to LES. The SBES model is an improved version of the DDES model with better boundary layer shielding and more pronounced RANS-LES switching capabilities. The success of such methods depends both on the capability of the underlying RANS model to accurately predict separation lines as well as on the switching characteristics of the hybrid model. The alternative is to apply LES over the entire car, typically using a wall-model, either as a classical wall-function or a thin RANS layer near the wall to reduce resolution requirements. It is important to notice that the usage of LES on under-resolved meshes can also compromise the accuracy of separation onset predictions. While requiring a higher resolution of the boundary layer, the advantage of LES versus hybrid models is the ‘seamless’ transition between attached and separated flow regions (no model switch). <br /> <br /> At the current point, it is not obvious which of these SRS approaches will gain the upper hand. Most likely, both approaches will be applied to provide the design engineer with a set of tools, with a variation in cost/performance ratio to be used during different phases of the design process. It is also likely that tunable RANS models (e.g. like the GEKO model by [https://www.researchgate.net/publication/336105262_Development_of_a_Generalized_K-o_Two-Equation_Turbulence_Model Menter et al. 2020]) or models based on machine learning) can get back into the mix for quick initial design studies. <br /> <br /> As a final comment, it should be noted that the Ahmed car body with slant angle of 25° is a highly sensitive test case due to its geometric proximity to a topological change of the flow. Even small modifications in model formulation, numerical settings or grid resolution can ‘flip’ the flow from one topology to another. Some of the sensitivities observed for that test case will therefore not necessarily be present in more realistic automotive configurations. <br /> <br /> =='''References'''==<br /> Menter, F. R., Matyushenko A., Lechner R.: Development of a generalized k-omega two-equation turbulence model. In Dillmann A. et al(eds) , New Results in Numerical and Experimental Fluid Mechanics XII, pp. 101-109. Springer (2020) <br /> <br /> <br /> © copyright ERCOFTAC 2004<br /> <br /> <br /> ----<br /> <br /> ''Contributors: Remi Manceau; Jean-Paul Bonnet - Université de Poitiers. &amp;mdash; Update (2024) F.R.Menter, ANSYS Germany '', <br /> <br /> <br /> {{AC|front=AC 1-05|description=Description_AC1-05|testdata=Test Data_AC1-05|cfdsimulations=CFD Simulations_AC1-05|evaluation=Evaluation_AC1-05|qualityreview=Quality Review_AC1-05|bestpractice=Best Practice Advice_AC1-05|relatedUFRs=Related UFRs_AC1-05}}</div> Mike https://kbwiki.ercoftac.org/w/index.php?title=Evaluation_AC1-05&diff=45214 Evaluation AC1-05 2024-02-14T09:47:07Z <p>Mike: </p> <hr /> <div>{{AC|front=AC 1-05|description=Description_AC1-05|testdata=Test Data_AC1-05|cfdsimulations=CFD Simulations_AC1-05|evaluation=Evaluation_AC1-05|qualityreview=Quality Review_AC1-05|bestpractice=Best Practice Advice_AC1-05|relatedUFRs=Related UFRs_AC1-05}}<br /> <br /> ='''Ahmed body'''=<br /> <br /> '''Application Challenge 1-05''' © copyright ERCOFTAC 2004<br /> <br /> <br /> <br /> =='''Comparison of Test data and CFD'''==<br /> <br /> Experiments provide very detailed data that offer a particularly difficult challenge to CFD. They showed that the drag crisis experienced by the body around 25°-30° is related to a dramatic change of the structure of the wake. The low-drag configuration (35°) consists in a massively separated wake, which is quasi-2D, while the high-drag configuration (25°) consists in a very complex, 3D wake structure, with a reattachment of the flow on the slant part and a strong interaction of the bubble with intense corner vortices, which are very energy-consuming.<br /> <br /> EXP1 shows that fixing a splitter plate in the wake of the body, in the symmetry plane, forces the flow to turn back to the low drag configuration (massively separated wake). The mechanism underlying these phenomena is not clear, but it could be due to the fact that the splitter plate counteracts a flapping of the wake in the span-wise direction. Therefore, there are some evidences that large-scale unsteadiness of the wake could play a crucial role in the wake structure transition. It could also explain high levels of turbulent stresses above the slant part that are very difficult to predict with steady-state RANS calculations.<br /> <br /> It appears from all the CFD results that the wake structure of the low drag configurations (35°) is correctly reproduced by all the turbulence models tested. The correct trend of the drag coefficient with the slant angle is correctly reproduced (CFD1), but the correct level is not found. In general, since the wake structure is correct, the pressure levels on the slant part are realistic, but the exact pressure repartition on the slant part and the vertical base are hardly reproduced.<br /> <br /> <br /> Concerning the high-drag configuration (25°), the great majority of the CFD computations were not able to reproduce the complex, 3D structure of the wake: a massively separated wake is obtained, which shows that the wake structure transition is missed. The number of computation and the variety of numerical schemes and meshes give many indications that the main issue is not numerical, but linked to the physical modeling: turbulence model and steady-state strategy. It appears that only two types of modeling are able to reproduce the structure of the wake: LES (CFD9) and low-Reynolds number Reynolds stress model (CFD13). It should indicate that the large-scale unsteadiness of the wake must be resolved (the potential of URANS has not been investigated extensively yet) or, alternatively, the absence of large-scale unsteadiness resolution must be compensated by a very refined turbulence modeling (Reynolds stress transport equations and integration down to the wall). However, these partial conclusions are only based on one LES and one low-Re RSM computation. Additional studies are necessary to confirm these favorable conclusions.<br /> <br /> <br /> The paper of Florian Menter extracted from the Proceedings of the 10th ERCOFTAC IAHR Workshop (http://www.ercoftac.nl/workshop10/index.html) with permission, gives a further comparison of experimental and CFD results, including various figures. This paper can be obtained by clicking [{{filepath:Ahmed.florian.menter.pdf}} here].<br /> <br /> ==='''Update added in 2024 by F.R. Menter'''===<br /> <br /> Since the ERCOFTAC workshops, simulations have progressed with an increased focus on Scale-Resolving Simulations. The simulations fall in two categories: Hybrid RANS-LES model and pure LES model simulations. Hybrid RANS-LES methods seem well suited for the Ahmed 25° car. They avoid the high cost of LES near the wall of the attached boundary layers. The ability of such models to predict the complex flow topology for the 25° case depends however on the ability of the underlying RANS model to predict separation from the slant onset. For a discussion of hybrid methods with application to this current test case see e.g. [https://hal.science/hal-02874819/document Guilminesau et al. (2020)], [https://www.sciencedirect.com/science/article/pii/S0167610520302117 Ekman et al. (2020)].<br /> <br /> The application of LES to the 25° case proved surprisingly difficult. Up to the publication by [https://link.springer.com/article/10.1007/s10494-023-00472-9 Menter et al (2024)] no LES with acceptable accuracy for the exp. Reynolds number has been achieved. For a review of LES studies see [https://link.springer.com/article/10.1007/s10494-023-00472-9 Menter et al (2024)]. Of special interest is that simulations at artificially reduced Reynolds number were able to predict the correct flow topology with separation and reattachment on the slant, even on coarse grids. However, at the exp. Reynolds number, the simulations showed a similar behavior to RANS models. In one set of simulations, the flow stayed attached (like with k- type models) and in another set, the flow stalled (like with SST type models). The authors in [https://link.springer.com/article/10.1007/s10494-023-00472-9 Menter et al (2024)] confirmed this observation, even for much finer meshes than used previously (e.g. a 560 million block-structured hexahedral mesh resulted in fully attached flow). Only after turning to Octree meshes, which allow a three-dimensional refinement towards the wall, could a sufficient resolution of the boundary layer be achieved to allow a reliable prediction of separation and reattachment on the slant. The following pictures are taken from [https://link.springer.com/article/10.1007/s10494-023-00472-9 Menter et al (2024)].<br /> <br /> {|align=&quot;center&quot;<br /> |[[Image:Ac1_05_figure_2.png|600px|center|]]<br /> |-<br /> |''Figure 2:'' Zoom of Octree meshes O1 and O2 near the roof-slant intersection. <br /> |}<br /> <br /> {|align=&quot;center&quot;<br /> |[[Image:Ac1_05_figure_3a.png|600px|center|]]<br /> |-<br /> |[[Image:Ac1_05_figure_3b.png|600px|center|]]<br /> |-<br /> |''Figure 3:'' Flow structure on roof-center plane for WALE O1(top) and WALE O2 (bottom) meshes showing contours of vorticity. <br /> |}<br /> <br /> {|align=&quot;center&quot;<br /> |[[Image:Ac1_05_figure_4.png|600px|center|]]<br /> |-<br /> |''Figure 4:'' Wall shear stress on the roof-center plane for WALE- O2 and WALE- O1 in comparison with SBES/RANS solution. <br /> |}<br /> <br /> <br /> Fig. 2 shows two Octree meshes near the roof-slant onset of the Ahmed car. The coarser mesh has 230 million and the refined mesh has 320 million cells. Both grids are formally of sufficient near-wall resolution for a wall-resolved LES (with ∆x^+=∆z^+≈35,∆y^+=1 in streamwise, spanwise and wall-normal direction respectively). However, the 320 million cell mesh (O1) has an overall finer mesh in the central part of the boundary layer. This results in a resolution of finer turbulence structures in the roof boundary layer as seen in Fig.3. The improved resolution brings the LES closer to the wall shear stress distribution (Cf) of the SST/SBES model which can serve as a reliable reference for the zero-pressure gradient flow in that region (Fig.4).<br /> <br /> <br /> {|align=&quot;center&quot;<br /> |[[Image:Ac1_05_figure_5.png|600px|center|]]<br /> |-<br /> |''Figure 5:'' Velocity profiles in center plane for WRLES on O1 and O2 grids, compared to experimental data. <br /> |}<br /> <br /> {|align=&quot;center&quot;<br /> |[[Image:Ac1_05_figure_6.png|600px|center|]]<br /> |-<br /> |''Figure 6:'' Stress profiles for streamwise coordinate in center plane for WRLES on O1 and O2 grids, compared to experimental data. <br /> |}<br /> <br /> Both meshes produce highly accurate representations of the separation bubble on the slant as seen from the velocity profiles in Fig. 5. Included in the figure is also a simulation on the O1 mesh where the WALE model was deactivated in the entire domain, which resulted in an even slightly better agreement with the experimental data. Fig. 6 shows the corresponding profiles for the streamwise stress component, which are again in good agreement with the experimental data, in contrast to RANS models which strongly underpredicted the stress level. While there are acceptable velocity profile results available for hybrid models e.g. [https://hal.science/hal-02874819/document Guilmineau et al. (2020)], also none of these simulations captures the correct stress-level, especially just downstream of the slant onset. This points to a high consistency of the depicted LES simulations. <br /> <br /> <br /> {|align=&quot;center&quot;<br /> |[[Image:Ac1_05_figure_7a.png|400px]][[Image:Ac1_05_figure_7b.png|400px]]<br /> |-<br /> |''Figure 7:'' : Flow topology on slant of Ahmed car. Left: experimental oil flow (from Ahmed et al 1984). Right: Octree O1 – no model simulation. <br /> |}<br /> <br /> Figure 7 shows the flow topology for the O1 (no model) simulation compared to the experimental oil flow. As expected from the close agreement in the velocity profiles, the agreement in the flow pattern is also very close. <br /> <br /> <br /> {|align=&quot;center&quot;<br /> |[[Image:Ac1_05_figure_8.png|600px|center|]]<br /> |-<br /> |''Figure 8:'' Q-criterion plots for Octree O1 no model solution. Large picture has &lt;math&gt;Q=5 \cdot 10^6s^{-2}&lt;/math&gt; and smaller picture has &lt;math&gt;Q=1 \cdot 10^8s^{-2}&lt;/math&gt;. <br /> |}<br /> <br /> Finally, Figure 8 shows the resolved turbulence structures using the Q-criterion with a zoom to the slant onset region for the O1 mesh. As seen, this mesh allows for a very fine resolution of the turbulence which is necessary to accurately capture flow reattachment. <br /> <br /> =='''References'''==<br /> Ekman , P., Wieser, D., Virdung, T., Karlsson, M., Assessment of hybrid RANS-LES methods for accurate aerodynamic simulations. J. of wind Engg. And Industrial Aerodynamics, 206, (2020), 104301.<br /> <br /> Guilmineau E., Deng G.B., Leroyer A., Queutey P. Visonneau M., Wackers J., Assessment of hybrid RANS-LES formulations for flow simulation around the Ahmed body. Comput. Fluids 176, 302-319 (2018) <br /> <br /> Menter,F.R., Hüppe A., Flad D., Garburak, A. V., Matyushenko A.A., Stabnikov A.S., Large eddy simulations for the Ahmed car at 25° slant angle at different Teynolds numbers. Flow, Turbulence and Combustion, 112, 321-343, (2024).<br /> <br /> © copyright ERCOFTAC 2004<br /> <br /> <br /> ----<br /> <br /> ''Contributors: Remi Manceau; Jean-Paul Bonnet - Université de Poitiers. &amp;mdash; Update (2024) F.R.Menter, ANSYS Germany '', <br /> <br /> <br /> {{AC|front=AC 1-05|description=Description_AC1-05|testdata=Test Data_AC1-05|cfdsimulations=CFD Simulations_AC1-05|evaluation=Evaluation_AC1-05|qualityreview=Quality Review_AC1-05|bestpractice=Best Practice Advice_AC1-05|relatedUFRs=Related UFRs_AC1-05}}</div> Mike https://kbwiki.ercoftac.org/w/index.php?title=CFD_Simulations_AC1-05&diff=45213 CFD Simulations AC1-05 2024-02-14T09:46:51Z <p>Mike: </p> <hr /> <div>{{AC|front=AC 1-05|description=Description_AC1-05|testdata=Test Data_AC1-05|cfdsimulations=CFD Simulations_AC1-05|evaluation=Evaluation_AC1-05|qualityreview=Quality Review_AC1-05|bestpractice=Best Practice Advice_AC1-05|relatedUFRs=Related UFRs_AC1-05}}<br /> <br /> ='''Ahmed body'''=<br /> <br /> '''Application Challenge 1-05''' © copyright ERCOFTAC 2004<br /> <br /> <br /> <br /> =='''Overview of CFD Simulations'''==<br /> <br /> CFD simulations have developed rapidly during the writing of the present document, during the MOVA consortium and in the frame of the 9th and 10th ERCOFTAC-IAHR Workshop on Refined Turbulence Modeling organized in Darmstad, Germany and Poitiers, France, in 2001 and 2002, respectively. These workshops were organized under the auspices of the Special Interest Group 15 on Turbulence Modeling of ERCOFTAC. The proceedings of the 10th ERCOFTAC-IAHR Workshop can be found at:<br /> <br /> [http://www.ercoftac.nl/workshop10/index.html http://www.ercoftac.nl/workshop10/index.html]<br /> <br /> For the 10th ERCOFTAC-IAHR Workshop, several recommendations were made to the groups participating in the CFD calculations. Among them the recommendation to extend the computational domain up to 5 times the car length downstream of the body, and the possibility to omit the stilts.<br /> <br /> Many of the CFD results are considered by the authors themselves as preliminary computations and were therefore not inserted into the knowledge base.<br /> <br /> The geometry is simple enough to be satisfactorily represented.<br /> <br /> =='''Simulation Case CFD1'''==<br /> <br /> ==='''Solution strategy CFD1'''===<br /> <br /> RANS modelling.<br /> <br /> Commercial FLUENT 4.2 code, based on unstructured finite volume discretization.<br /> <br /> Reynolds number: 4.29x106 (see EXP1). Steady state computation.<br /> <br /> The slant angle is varied from 0 to 50 degrees.<br /> <br /> <br /> ==='''Computational Domain CFD1'''===<br /> <br /> Symmetry is used to compute half the domain.<br /> <br /> Domain: [-3L;5L]x[0;2L]x[0;2L]<br /> <br /> Mesh : 450,000 cells<br /> <br /> Approximate value of y+ on solid surfaces : 30.<br /> <br /> <br /> ==='''Boundary Conditions CFD1'''===<br /> <br /> Inlet: turbulence level 0.5% with a mixing length of 5x10-3m.<br /> <br /> Outlet: constant pressure.<br /> <br /> Solid boundaries: wall functions<br /> <br /> Symmetry plane: symmetry<br /> <br /> Other boundaries: no details<br /> <br /> <br /> ==='''Application of Physical Models CFD1'''===<br /> <br /> Standard K-ε model with standard wall functions.<br /> <br /> <br /> ==='''Numerical Accuracy CFD1'''===<br /> <br /> Mesh refinement is performed until the drag reaches a constant value.<br /> <br /> Convection scheme : 2nd order.<br /> <br /> <br /> ==='''CFD Results CFD1'''===<br /> <br /> Friction lines, pressure iso-contours at the model surface, velocity vector fields, drag coefficient.<br /> <br /> =='''References CFD1'''==<br /> <br /> '''Modelling of stationnary three-dimensional separated flows around an Ahmed reference model.'''<br /> <br /> P. Gilliéron, F. Chometon, ESAIM proc., vol 7, 173-182, 1999<br /> <br /> <br /> =='''Simulation Case CFD2'''==<br /> <br /> ==='''Solution strategy CFD2'''===<br /> <br /> RANS modeling.<br /> <br /> Commercial FLUENT 5 code based on unstructured finite volume discretization.<br /> <br /> Reynolds number: 4.29x106 (see EXP1). Steady state computation.<br /> <br /> Slant angle: 30°.<br /> <br /> ==='''Computational Domain CFD2'''===<br /> <br /> Symmetry is used to compute half the domain. Stilts are included.<br /> <br /> Domain: no details.<br /> <br /> Mesh : 704,000 cells.<br /> <br /> y+ at the first grid point from the wall of order of 50 - 350.<br /> <br /> ==='''Boundary Conditions CFD2'''===<br /> <br /> No details.<br /> <br /> ==='''Application of Physical Models CFD2'''===<br /> <br /> - Standard k-ε model with non-equilibrium wall functions.<br /> <br /> - RSM (no details) with non-equilibrium wall functions.<br /> <br /> ==='''Numerical Accuracy CFD2'''===<br /> <br /> No details.<br /> <br /> ==='''CFD Results CFD2'''===<br /> <br /> Pathlines and velocities.<br /> <br /> Aerodynamic drag coefficient.<br /> <br /> =='''References CFD2'''==<br /> <br /> Advances in external-aero simulation of ground vehicles using the steady RANS equation.<br /> <br /> Makowski F.T and Kim S.E., SAE Conf 2000-01-0484<br /> <br /> <br /> =='''Simulation Case CFD3'''==<br /> <br /> ==='''Solution strategy CFD3'''===<br /> <br /> '''Large-eddy simulation.'''<br /> <br /> In house code PRICELES, based on unstructured second-order finite-element discretization.<br /> <br /> Reynolds number= 4.29 x106<br /> <br /> Slant angle: 28°.<br /> <br /> ==='''Computational Domain CFD3'''===<br /> <br /> Domain: [-3L;5L]x[-L;L]x[-LxL] (the ground plate is NOT included: the body is suspended in the middle of the domain).<br /> <br /> Mesh: 1.6x106 cells.<br /> <br /> y+ at the first grid point from the wall is about 80 (averaged value).<br /> <br /> ==='''Boundary Conditions CFD3'''===<br /> <br /> Inlet: constant velocity.<br /> <br /> Outlet: constant pressure conditions.<br /> <br /> Solid boundaries: wall functions<br /> <br /> Other boundaries : symmetry.<br /> <br /> ==='''Application of Physical Models CFD3'''===<br /> <br /> Sub-grid model: standard Smagorinsky.<br /> <br /> ==='''Numerical Accuracy CFD3'''===<br /> <br /> Second-order convection scheme and time marching (CFL number=3).<br /> <br /> ==='''CFD Results CFD3'''===<br /> <br /> '''Pressure, pressure coef., velocity, drag coef, Q-criterion contours, vorticity.'''<br /> <br /> =='''References CFD3'''==<br /> <br /> Large eddy simulation of an Ahmed reference model.<br /> <br /> R.J.A. Howard, M. Pourquie.<br /> <br /> Journal of Turbulence, 2002<br /> <br /> <br /> =='''Simulation Case CFD4'''==<br /> <br /> ==='''Solution strategy CFD4'''===<br /> <br /> RANS modelling.<br /> <br /> Commercial AVL SWIFT code, based on unstructured finite volume discretization.<br /> <br /> Reynolds number: 2.78x106 (see EXP2). Steady state computation.<br /> <br /> Slant angle: 25° and 35°.<br /> <br /> ==='''Computational Domain CFD4'''===<br /> <br /> Symmetry is used to compute half the domain.<br /> <br /> Domain: Inlet at -1.5L. No other details.<br /> <br /> Mesh : 530,000 cells.<br /> <br /> y+ on solid surfaces &lt; 100.<br /> <br /> ==='''Boundary Conditions CFD4'''===<br /> <br /> Inlet: interpolated experimental profile at –1.4L used at –1.5L.<br /> <br /> Solid boundaries: wall functions<br /> <br /> Symmetry plane: symmetry<br /> <br /> Other boundaries: no details<br /> <br /> ==='''Application of Physical Models CFD4'''===<br /> <br /> - Standard k-ε model with standard wall functions.<br /> <br /> - SSG Reynolds stress model with standard wall functions<br /> <br /> - Hybrid k-ε/Reynolds stress model (coefficient Cm of the k-ε model obtained from Reynolds stress transport equations) with standard wall functions<br /> <br /> ==='''Numerical Accuracy CFD4'''===<br /> <br /> Grid sensitivity study.<br /> <br /> Study of the influence of the convection scheme.<br /> <br /> ==='''CFD Results CFD4'''===<br /> <br /> Cp, velocity profiles in the boundary layer over the slant part.<br /> <br /> =='''References CFD4'''==<br /> <br /> B. Basara, S. Jakirlic, Flow Around a simplified car body (Ahmed body) : description of numerical methodology, in : S. Jakirlic, R. Jester-Zürker, C. Tropea, editors, 9th ERCOFTAC/IAHR/COST Workshop on Refined Turbulence Modelling, Oct. 4-5, 2001, Darmstadt University of Technology, Germany.<br /> <br /> <br /> =='''Simulation Case CFD5'''==<br /> <br /> =='''Solution strategy CFD5'''==<br /> <br /> RANS modelling.<br /> <br /> In-house code Saturne, based on unstructured finite volume discretization.<br /> <br /> Reynolds number: 2.78x106 (see EXP2). Steady state computation.<br /> <br /> Slant angle: 25° and 35°.<br /> <br /> ==='''Computational Domain CFD5'''===<br /> <br /> Full body (no symmetry used)<br /> <br /> Domain: no details<br /> <br /> Mesh : 300,000 cells<br /> <br /> y+ on solid surfaces : no details.<br /> <br /> ==='''Boundary Conditions CFD5'''===<br /> <br /> Inlet: no details.<br /> <br /> Solid boundaries: wall functions<br /> <br /> Other boundaries: no details<br /> <br /> ==='''Application of Physical Models CFD5'''===<br /> <br /> - Standard k-ε model with standard wall functions<br /> <br /> - Launder, Reece, Rodi (IP) Reynolds stress model with standard wall functions<br /> <br /> - Linearized production k-ε model with standard wall functions<br /> <br /> <br /> ==='''Numerical Accuracy CFD5'''===<br /> <br /> Convection scheme : 80% central differencing (2nd order), 20% upwind differencing (1st order).<br /> <br /> ==='''CFD Results CFD5'''===<br /> <br /> Cp, velocity profiles in the boundary layer over the slant part.<br /> <br /> Vector plots, turbulent energy contours, streamlines.<br /> <br /> =='''References CFD5'''==<br /> <br /> S. Tekam, D. Laurence, T. Buchal, Flow around the Ahmed body, in : S. Jakirlic, R. Jester-Zürker, C. Tropea, editors, 9th ERCOFTAC/ IAHR/ COST Workshop on Refined Turbulence Modelling, Oct. 4-5, 2001, Darmstadt University of Technology, Germany.<br /> <br /> <br /> =='''Simulation Case CFD6'''==<br /> <br /> ==='''Solution strategy CFD6'''===<br /> <br /> RANS modelling.<br /> <br /> Commercial FLUENT code, based on unstructured finite volume discretization.<br /> <br /> Reynolds number: 2.78x106 (see EXP2). Steady state computation.<br /> <br /> Slant angle: 25°.<br /> <br /> ==='''Computational Domain CFD6'''===<br /> <br /> Domain: no details<br /> <br /> Mesh : 2.3x106 cells<br /> <br /> y+ on solid surfaces : no details<br /> <br /> ==='''Boundary Conditions CFD6'''===<br /> <br /> Solid boundaries:<br /> <br /> - non-equilibrium wall functions for the k-ε model<br /> <br /> - no slip walls for the SST model<br /> <br /> <br /> <br /> Inlet, outlet and other boundaries: no details<br /> <br /> ==='''Application of Physical Models CFD6'''===<br /> <br /> - Realizable k-ε model with non-equilibrium wall functions<br /> <br /> - SST model<br /> <br /> ==='''Numerical Accuracy CFD6'''===<br /> <br /> No details<br /> <br /> ==='''CFD Results CFD6'''===<br /> <br /> Cp, velocity profiles in the boundary layer over the slant part.<br /> <br /> =='''References CFD6'''==<br /> <br /> M. Lanfrit, M. Braun, D. Cokljat, Contribution to case 9.4: Ahmed body, in : S. Jakirlic, R. Jester-Zürker, C. Tropea, editors, 9th ERCOFTAC/ IAHR/ COST Workshop on Refined Turbulence Modelling, Oct. 4-5, 2001, Darmstadt University of Technology, Germany.<br /> <br /> <br /> =='''Simulation Case CFD7'''==<br /> <br /> ==='''Solution strategy CFD7'''===<br /> <br /> RANS modelling in unsteady mode.<br /> <br /> In-house X-Stream code, based on finite volume solver for multi block structured non-orthogonal, curvilinear grid with collocated data arrangement. The convection terms are discretized using hybrid scheme with more than 60% central differencing. The diffusion terms are approximated with central differences. The SIMPLE method is used for the pressure-velocity coupling.<br /> <br /> Reynolds number: 2.78x106 (see EXP2).<br /> <br /> Slant angle: 35°<br /> <br /> ==='''Computational Domain CFD7'''===<br /> <br /> Full body (no symmetry condition used).<br /> <br /> Domain: [-2L;5L]x[-1.2;1.2L]x[0;1.3L]<br /> <br /> 9th ERCOFTAC workshop: 500,000 cells<br /> <br /> 10th ERCOFTAC workshop: 2 meshes: 490,000 and 820,000 cells (fine mesh used for the k-ε model only)<br /> <br /> Approximate value of y+ on solid surfaces:<br /> <br /> - 9th workshop: 60<br /> <br /> - 10th workshop: 17 (coarse mesh) and 11 (fine mesh).<br /> <br /> ==='''Boundary Conditions CFD7'''===<br /> <br /> Inlet: turbulence intensity=2,5%<br /> <br /> Solid boundaries: wall functions<br /> <br /> Outlet: no details<br /> <br /> Other boundaries: no details<br /> <br /> ==='''Application of Physical Models CFD7'''===<br /> <br /> 9th ERCOFTAC workshop:<br /> <br /> - Standard k-ε model with standard wall functions<br /> <br /> - SSG Reynolds stress model with standard wall functions<br /> <br /> - SSS Reynolds stress model with non-equilibrium wall functions<br /> <br /> - V2F model with wall functions<br /> <br /> - Elliptic blending model (Reynolds stress model) with wall functions<br /> <br /> <br /> <br /> 10th ERCOFTAC workshop:<br /> <br /> - Standard k-ε model with wall functions<br /> <br /> - V2F model with wall functions<br /> <br /> - SSG Reynolds stress model with modified ε equation (Hanjalic, Jakirlic) and standard wall functions<br /> <br /> ==='''Numerical Accuracy CFD7'''===<br /> <br /> Convection scheme : 60% 2nd order central differencing, 40% 1st order upwind differencing.<br /> <br /> ==='''CFD Results CFD7'''===<br /> <br /> Cp contours on the slant part, velocity profiles in the boundary layer over the slant part, vectors plots in 13 planes (see EXP2).<br /> <br /> ==''References CFD7'''==<br /> <br /> O. Ouhlous, W. Khier, Y. Liu, K. Hanjalic, in: S. Jakirlic, R. Jester-Zürker, C. Tropea, editors, 9th ERCOFTAC/ IAHR/ COST Workshop on Refined Turbulence Modelling, Oct. 4-5, 2001, Darmstadt University of Technology, Germany.<br /> <br /> <br /> <br /> M. Hadziabdic, K. Hanjalic, W. Khier, Y. Liu, O. Ouhlous, Flow around a simplified car body (Ahmed car model), in: R. Manceau, J.-P. Bonnet, editors, 10th ERCOFTAC (SIG-15)/IAHR/QNET-CFD Workshop on Refined Turbulence Modelling, Oct. 10-11, 2002, Laboratoire d’études aérodynamiques, UMR CNRS 6609, Université de Poitiers, France.<br /> <br /> <br /> =='''Simulation Case CFD8'''==<br /> <br /> ==='''Solution strategy CFD8'''===<br /> <br /> RANS modelling.<br /> <br /> In-house code STREAM, which is a finite volume solver which uses a structured, non-orthogonal curvilinear, multi block grid and a fully collocated arrangement. The SIMPLE pressure correction method and Rie &amp; Chow interpolation are used to prevent unrealistic pressure fluctuations. The convection terms are discretized using an upwind scheme or a TVD scheme based on the third-order QUICK scheme.<br /> <br /> Reynolds number: 2.78x106 (see EXP2). Steady state computation.<br /> <br /> Slant angle: 25° and 35°.<br /> <br /> ==='''Computational Domain CFD8'''===<br /> <br /> Symmetry is used to compute half the domain. Stilts not included.<br /> <br /> Domain: [-2L;4L]x[0;L]x[0;L]<br /> <br /> Mesh : 300,000 cells<br /> <br /> Approximate value of y+ on solid surfaces : between 55 and 550.<br /> <br /> ==='''Boundary Conditions CFD8'''===<br /> <br /> Inlet:<br /> <br /> - U=38.51 m/s (based on the experimental profile at –1.4L in order to account for the flow deceleration in front of the body)<br /> <br /> - K=6.58x10-3 m2 s-2<br /> <br /> - nt/n=10 (influence tested)<br /> <br /> <br /> <br /> Outflow: zero gradients for all variables<br /> <br /> Solid boundaries: wall functions<br /> <br /> Symmetry plane: symmetry<br /> <br /> Other boundaries: symmetry<br /> <br /> ==='''Application of Physical Models CFD8'''===<br /> <br /> - Standard k-ε model with Yap correction and SCL wall functions (see below)<br /> <br /> - Standard k-ε model with Yap correction and UMIST-N wall functions<br /> <br /> - Linear realizable k-ε model with SCL wall functions<br /> <br /> - Linear realizable k-ε model with UMIST-A wall functions<br /> <br /> - Nonlinear k-ε model (Craft et al.) with SCL wall functions<br /> <br /> - Nonlinear k-ε model (Craft et al.) with UMIST-A wall functions<br /> <br /> <br /> <br /> Wall functions:<br /> <br /> - SCL = Simplified Chieng and Launder<br /> <br /> - UMIST-A = UMIST Analytical<br /> <br /> - UMIST-N = UMIST Numerical<br /> <br /> ==='''Numerical Accuracy CFD8'''===<br /> <br /> Convection scheme : 3rd order Quick scheme (UMIST) or 1st order upwind scheme in case of numerical instability.<br /> <br /> Tests were made to assess iteration convergence. Some unsteady calculations were made too. A coarser grid was used to obtain some information on grid dependency.<br /> <br /> ==='''CFD Results CFD8'''===<br /> <br /> Cp contours on the slant part, velocity profiles in the boundary layer over the slant part, vectors plots in 13 planes (see EXP2).<br /> <br /> =='''References CFD8'''==<br /> <br /> T.J. Craft, S.E. Gant, H. Iacovides, B.E. Launder, C.M.E. Robinson, Computational methods applied to the study of flow around a simplified “Ahmed” car body, in: R. Manceau, J.-P. Bonnet, editors, 10th ERCOFTAC (SIG-15)/IAHR/QNET-CFD Workshop on Refined Turbulence Modelling, Oct. 10-11, 2002, Laboratoire d’études aérodynamiques, UMR CNRS 6609, Université de Poitiers, France.<br /> <br /> <br /> =='''Simulation Case CFD9'''==<br /> <br /> ==='''Solution strategy CFD9'''===<br /> <br /> LES.<br /> <br /> In-house code LESOCC2, based on block-structured finite volume discretization. A collocated cell arrangement was used employing the Rhie and Chow momentum interpolation procedure. The SIMPLE scheme was used for the pressure-velocity coupling, and the pressure correction equation was solved using the SIP method. Fluxes were discretized in space using a second order central difference scheme. The equations were integrated in time using a second order Runge Kutta scheme with an adaptive time step, employing a maximum CFL number of 0.6.<br /> <br /> Reynolds number: 2.78x106 (see EXP2).<br /> <br /> Slant angle: 25°.<br /> <br /> ==='''Computational Domain CFD9'''===<br /> <br /> Domain: [-2.2L;4.8L]x[-0.9L;0.9L]x[0;1.35L]. Ground plate and stilts included.<br /> <br /> Mesh :18.5x106 cells<br /> <br /> y+ on solid surfaces : no details<br /> <br /> ==='''Boundary Conditions CFD9'''===<br /> <br /> Inlet: constant velocity<br /> <br /> Outlet: convective outlet.<br /> <br /> Solid boundaries: wall functions<br /> <br /> Other boundaries: slip walls<br /> <br /> ==='''Application of Physical Models CFD9'''===<br /> <br /> Subgrid scale model: Smagorinky<br /> <br /> ==='''Numerical Accuracy CFD9'''===<br /> <br /> 2nd order convection scheme and time marching (CFL number &lt; 0.6)<br /> <br /> ==='''CFD Results CFD9'''===<br /> <br /> Cp contours on the slant part, velocity profiles in the boundary layer over the slant part, vectors plots in 13 planes (see EXP2).<br /> <br /> =='''References CFD9'''==<br /> <br /> C. Hinterberger, M. Garcia-Villalba, W. Rodi, Flow around a simplified car body. LES with wall functions, in: R. Manceau, J.-P. Bonnet, editors, 10th ERCOFTAC (SIG-15)/IAHR/QNET-CFD Workshop on Refined Turbulence Modelling, Oct. 10-11, 2002, Laboratoire d’études aérodynamiques, UMR CNRS 6609, Université de Poitiers, France.<br /> <br /> <br /> =='''Simulation Case CFD10'''==<br /> <br /> ==='''Solution strategy CFD10'''===<br /> <br /> RANS modelling.<br /> <br /> Commercial HEXANS CFD code, based on unstructured finite volume discretization. The convective fluxes are discretized using a centered scheme with 2nd and 4th order artificial dissipation. Diffusive fluxes are computed on pyramidal elements. The equations are integrated in time using the explicit Runge Kutta scheme. Local time stepping, multi grid and low-mach number preconditioning are used to accelerate the convergence to steady state. A mesh adaptation procedure is used in which the grid cells are refined by splitting it in 2, 4 or 8 subcells. The mesh adaptation is governed by criteria based on the flow physics, geometry or error estimates.<br /> <br /> Reynolds number: 2.78x106 (see EXP2). Steady state computation.<br /> <br /> Slant angle: 25°.<br /> <br /> ==='''Computational Domain CFD10'''===<br /> <br /> Symmetry is used to compute half the domain. Ground plate included, no stilts.<br /> <br /> Domain: [-2L;5L]x[0;0.9L]x[0;1.35L]<br /> <br /> Final Mesh : 815,000 cells<br /> <br /> Approximate value of y+ on solid surfaces : 1<br /> <br /> ==='''Boundary Conditions CFD10'''===<br /> <br /> Inflow: turbulence level 1%. nt/n = 1.<br /> <br /> Solid boundaries: no-slip walls<br /> <br /> Symmetry plane: symmetry<br /> <br /> Other boundaries: no details<br /> <br /> ==='''Application of Physical Models CFD10'''===<br /> <br /> Low-Reynolds number K-ε model (Yang-Shih).<br /> <br /> ==='''Numerical Accuracy CFD10'''===<br /> <br /> Mesh adaptation applied.<br /> <br /> Convection scheme : 2nd order.<br /> <br /> ==='''CFD Results CFD10'''===<br /> <br /> Cp contours on the slant part, velocity profiles in the boundary layer over the slant part, vectors plots in 13 planes (see EXP2).<br /> <br /> =='''References CFD10'''==<br /> <br /> B. Leonard, Ch. Hirsch, K. Kovalev, M. Elsden, K. Hillewaert, A. Patel, Flow around a simplified car body (Ahmed body), in: R. Manceau, J.-P. Bonnet, editors, 10th ERCOFTAC (SIG-15)/IAHR/QNET-CFD Workshop on Refined Turbulence Modelling, Oct. 10-11, 2002, Laboratoire d’études aérodynamiques, UMR CNRS 6609, Université de Poitiers, France.<br /> <br /> <br /> =='''Simulation Case CFD11'''==<br /> <br /> ==='''Solution strategy CFD11'''===<br /> <br /> RANS modelling.<br /> <br /> Commercial CFX-5 code, based on an unstructured, vertex based finite volume method. Co-located variables are used. The solver is second order accurate in space and time. The Rhie-Chow velocity pressure coupling is used. An implicit solver with algebraic multi grid is used to converge the equations to steady state.<br /> <br /> Reynolds number: 2.78x106 (see EXP2). Transient computation (steady solution obtained).<br /> <br /> Slant angle: 25° and 35°.<br /> <br /> ==='''Computational Domain CFD11'''===<br /> <br /> Symmetry is used to compute half the domain. No stilts included.<br /> <br /> Domain: [-3L;6L]x[0;0.9L]x[0;1.15L]<br /> <br /> The ground plate starts 2L in front of the body in order that the boundary layer approaching the body matches the experimental profile.<br /> <br /> Mesh : 2,5x106 cells<br /> <br /> Approximate value of y+ on solid surfaces : 1<br /> <br /> ==='''Boundary Conditions CFD11'''===<br /> <br /> Inlet: turbulence intensity=1%, nt/n=1.<br /> <br /> Solid boundaries:<br /> <br /> - SST model: no slip walls<br /> <br /> - Others: scalable wall functions<br /> <br /> Outlet: constant pressure<br /> <br /> Other boundaries: opening boundary conditions.<br /> <br /> ==='''Application of Physical Models CFD11'''===<br /> <br /> - Standard k-ε model with scalable wall functions<br /> <br /> - SST model<br /> <br /> - SSG Reynolds stress model with scalable wall functions<br /> <br /> ==='''Numerical Accuracy CFD11'''===<br /> <br /> Convection scheme: 2nd order.<br /> <br /> Studies of the influence of the following parameters are performed:<br /> <br /> Mesh refinement, formulation of the boundary conditions (opening vs. slip walls), advection scheme.<br /> <br /> ==='''CFD Results CFD11'''===<br /> <br /> The same quantities (except for triple correlations) as for experiment EXP2 are available in the Knowledge Base : results for the mean velocities U, V, W, Reynolds stresses [[Image:Image23.gif]] [[Image:Image24.gif]] [[Image:Image25.gif]] [[Image:Image26.gif]] [[Image:Image27.gif]] in some planes and profiles in the boundary layer above the slant part:<br /> <br /> <br /> <br /> <br /> '''k-epsilon model'''<br /> <br /> 25° slant angle:<br /> <br /> planes:<br /> &lt;span class=&quot;plainlinks&quot;&gt;[{{filepath:CFD11_KEPS_Ahmed_25_y=0.dat}} y=0]&lt;/span&gt;;<br /> &lt;span class=&quot;plainlinks&quot;&gt;[{{filepath:CFD11_KEPS_Ahmed_25_y=100.dat}} y=100]&lt;/span&gt;; <br /> &lt;span class=&quot;plainlinks&quot;&gt;[{{filepath:CFD11_KEPS_Ahmed_25_y=180.dat}} y=180]&lt;/span&gt;;<br /> <br /> &lt;span class=&quot;plainlinks&quot;&gt;[{{filepath:CFD11_KEPS_Ahmed_25_y=195.dat}} y=195]&lt;/span&gt;;<br /> &lt;span class=&quot;plainlinks&quot;&gt;[{{filepath:CFD11_KEPS_Ahmed_25_z=360.dat}} z=360]&lt;/span&gt;<br /> <br /> &lt;span class=&quot;plainlinks&quot;&gt;[{{filepath:CFD11_KEPS_Ahmed_25_x=-794.dat}} x=-794]&lt;/span&gt;;<br /> &lt;span class=&quot;plainlinks&quot;&gt;[{{filepath:CFD11_KEPS_Ahmed_25_x=-178.dat}} x=-178]&lt;/span&gt;;<br /> &lt;span class=&quot;plainlinks&quot;&gt;[{{filepath:CFD11_KEPS_Ahmed_25_x=-138.dat}} x=-138]&lt;/span&gt;;<br /> &lt;span class=&quot;plainlinks&quot;&gt;[{{filepath:CFD11_KEPS_Ahmed_25_x=-88.dat}} x=-88]&lt;/span&gt;;<br /> &lt;span class=&quot;plainlinks&quot;&gt;[{{filepath:CFD11_KEPS_Ahmed_25_x=-38.dat}} x=-38]&lt;/span&gt;;<br /> &lt;span class=&quot;plainlinks&quot;&gt;[{{filepath:CFD11_KEPS_Ahmed_25_x=0.dat}} x=0]&lt;/span&gt;;<br /> &lt;span class=&quot;plainlinks&quot;&gt;[{{filepath:CFD11_KEPS_Ahmed_25_x=80.dat}} x=80]&lt;/span&gt;;<br /> &lt;span class=&quot;plainlinks&quot;&gt;[{{filepath:CFD11_KEPS_Ahmed_25_x=200.dat}} x=200]&lt;/span&gt;;<br /> &lt;span class=&quot;plainlinks&quot;&gt;[{{filepath:CFD11_KEPS_Ahmed_25_x=500.dat}} x=500]&lt;/span&gt;<br /> <br /> profiles in the boundary layer:<br /> &lt;span class=&quot;plainlinks&quot;&gt;[{{filepath:CFD11_KEPS_Ahmed_25_BL_x=-243.dat}} x=-243]&lt;/span&gt;,<br /> &lt;span class=&quot;plainlinks&quot;&gt;[{{filepath:CFD11_KEPS_Ahmed_25_BL_x=-223.dat}} -223]&lt;/span&gt;,<br /> &lt;span class=&quot;plainlinks&quot;&gt;[{{filepath:CFD11_KEPS_Ahmed_25_BL_x=-203.dat}} -203]&lt;/span&gt;,<br /> &lt;span class=&quot;plainlinks&quot;&gt;[{{filepath:CFD11_KEPS_Ahmed_25_BL_x=-183.dat}} -183]&lt;/span&gt;,<br /> &lt;span class=&quot;plainlinks&quot;&gt;[{{filepath:CFD11_KEPS_Ahmed_25_BL_x=-163.dat}} -163]&lt;/span&gt;,<br /> &lt;span class=&quot;plainlinks&quot;&gt;[{{filepath:CFD11_KEPS_Ahmed_25_BL_x=-143.dat}} -143]&lt;/span&gt;,<br /> &lt;span class=&quot;plainlinks&quot;&gt;[{{filepath:CFD11_KEPS_Ahmed_25_BL_x=-123.dat}} -123]&lt;/span&gt;,<br /> &lt;span class=&quot;plainlinks&quot;&gt;[{{filepath:CFD11_KEPS_Ahmed_25_BL_x=-103.dat}} -103]&lt;/span&gt;,<br /> &lt;span class=&quot;plainlinks&quot;&gt;[{{filepath:CFD11_KEPS_Ahmed_25_BL_x=-83.dat}} -83]&lt;/span&gt;,<br /> &lt;span class=&quot;plainlinks&quot;&gt;[{{filepath:CFD11_KEPS_Ahmed_25_BL_x=-63.dat}} -63]&lt;/span&gt;,<br /> &lt;span class=&quot;plainlinks&quot;&gt;[{{filepath:CFD11_KEPS_Ahmed_25_BL_x=-43.dat}} -43]&lt;/span&gt;,<br /> &lt;span class=&quot;plainlinks&quot;&gt;[{{filepath:CFD11_KEPS_Ahmed_25_BL_x=-23.dat}} -23]&lt;/span&gt;,<br /> &lt;span class=&quot;plainlinks&quot;&gt;[{{filepath:CFD11_KEPS_Ahmed_25_BL_x=-3.dat}} -3]&lt;/span&gt;<br /> <br /> Pressure coefficients on the rear of the body:<br /> &lt;span class=&quot;plainlinks&quot;&gt;[{{filepath:CFD11_KEPS_Ahmed_25_Cp.dat}} Cp]&lt;/span&gt;<br /> <br /> <br /> <br /> 35° slant angle:<br /> <br /> planes:<br /> &lt;span class=&quot;plainlinks&quot;&gt;[{{filepath:CFD11_KEPS_Ahmed_35_y=0.dat}} y=0]&lt;/span&gt;;<br /> &lt;span class=&quot;plainlinks&quot;&gt;[{{filepath:CFD11_KEPS_Ahmed_35_y=100.dat}} y=100]&lt;/span&gt;; <br /> &lt;span class=&quot;plainlinks&quot;&gt;[{{filepath:CFD11_KEPS_Ahmed_35_y=180.dat}} y=180]&lt;/span&gt;;<br /> <br /> &lt;span class=&quot;plainlinks&quot;&gt;[{{filepath:CFD11_KEPS_Ahmed_35_y=195.dat}} y=195]&lt;/span&gt;;<br /> &lt;span class=&quot;plainlinks&quot;&gt;[{{filepath:CFD11_KEPS_Ahmed_35_z=360.dat}} z=360]&lt;/span&gt;<br /> <br /> &lt;span class=&quot;plainlinks&quot;&gt;[{{filepath:CFD11_KEPS_Ahmed_35_x=-794.dat}} x=-794]&lt;/span&gt;;<br /> &lt;span class=&quot;plainlinks&quot;&gt;[{{filepath:CFD11_KEPS_Ahmed_35_x=-178.dat}} x=-178]&lt;/span&gt;;<br /> &lt;span class=&quot;plainlinks&quot;&gt;[{{filepath:CFD11_KEPS_Ahmed_35_x=-138.dat}} x=-138]&lt;/span&gt;;<br /> &lt;span class=&quot;plainlinks&quot;&gt;[{{filepath:CFD11_KEPS_Ahmed_35_x=-88.dat}} x=-88]&lt;/span&gt;;<br /> &lt;span class=&quot;plainlinks&quot;&gt;[{{filepath:CFD11_KEPS_Ahmed_35_x=-38.dat}} x=-38]&lt;/span&gt;;<br /> &lt;span class=&quot;plainlinks&quot;&gt;[{{filepath:CFD11_KEPS_Ahmed_35_x=0.dat}} x=0]&lt;/span&gt;;<br /> &lt;span class=&quot;plainlinks&quot;&gt;[{{filepath:CFD11_KEPS_Ahmed_35_x=80.dat}} x=80]&lt;/span&gt;;<br /> &lt;span class=&quot;plainlinks&quot;&gt;[{{filepath:CFD11_KEPS_Ahmed_35_x=200.dat}} x=200]&lt;/span&gt;;<br /> &lt;span class=&quot;plainlinks&quot;&gt;[{{filepath:CFD11_KEPS_Ahmed_35_x=500.dat}} x=500]&lt;/span&gt;<br /> <br /> profiles in the boundary layer:<br /> &lt;span class=&quot;plainlinks&quot;&gt;[{{filepath:CFD11_KEPS_Ahmed_35_BL_x=-243.dat}} x=-243]&lt;/span&gt;,<br /> &lt;span class=&quot;plainlinks&quot;&gt;[{{filepath:CFD11_KEPS_Ahmed_35_BL_x=-223.dat}} -223]&lt;/span&gt;,<br /> &lt;span class=&quot;plainlinks&quot;&gt;[{{filepath:CFD11_KEPS_Ahmed_35_BL_x=-203.dat}} -203]&lt;/span&gt;,<br /> &lt;span class=&quot;plainlinks&quot;&gt;[{{filepath:CFD11_KEPS_Ahmed_35_BL_x=-183.dat}} -183]&lt;/span&gt;,<br /> &lt;span class=&quot;plainlinks&quot;&gt;[{{filepath:CFD11_KEPS_Ahmed_35_BL_x=-163.dat}} -163]&lt;/span&gt;,<br /> &lt;span class=&quot;plainlinks&quot;&gt;[{{filepath:CFD11_KEPS_Ahmed_35_BL_x=-143.dat}} -143]&lt;/span&gt;,<br /> &lt;span class=&quot;plainlinks&quot;&gt;[{{filepath:CFD11_KEPS_Ahmed_35_BL_x=-123.dat}} -123]&lt;/span&gt;,<br /> &lt;span class=&quot;plainlinks&quot;&gt;[{{filepath:CFD11_KEPS_Ahmed_35_BL_x=-103.dat}} -103]&lt;/span&gt;,<br /> &lt;span class=&quot;plainlinks&quot;&gt;[{{filepath:CFD11_KEPS_Ahmed_35_BL_x=-83.dat}} -83]&lt;/span&gt;,<br /> &lt;span class=&quot;plainlinks&quot;&gt;[{{filepath:CFD11_KEPS_Ahmed_35_BL_x=-63.dat}} -63]&lt;/span&gt;,<br /> &lt;span class=&quot;plainlinks&quot;&gt;[{{filepath:CFD11_KEPS_Ahmed_35_BL_x=-43.dat}} -43]&lt;/span&gt;,<br /> &lt;span class=&quot;plainlinks&quot;&gt;[{{filepath:CFD11_KEPS_Ahmed_35_BL_x=-23.dat}} -23]&lt;/span&gt;,<br /> &lt;span class=&quot;plainlinks&quot;&gt;[{{filepath:CFD11_KEPS_Ahmed_35_BL_x=-3.dat}} -3]&lt;/span&gt;<br /> <br /> Pressure coefficients on the rear of the body:<br /> &lt;span class=&quot;plainlinks&quot;&gt;[{{filepath:CFD11_KEPS_Ahmed_35_Cp.dat}} Cp]&lt;/span&gt;<br /> <br /> <br /> <br /> '''SST model'''<br /> <br /> 25° slant angle:<br /> <br /> planes:<br /> &lt;span class=&quot;plainlinks&quot;&gt;[{{filepath:CFD11_SST_Ahmed_25_y=0.dat}} y=0]&lt;/span&gt;;<br /> &lt;span class=&quot;plainlinks&quot;&gt;[{{filepath:CFD11_SST_Ahmed_25_y=100.dat}} y=100]&lt;/span&gt;; <br /> &lt;span class=&quot;plainlinks&quot;&gt;[{{filepath:CFD11_SST_Ahmed_25_y=180.dat}} y=180]&lt;/span&gt;;<br /> <br /> &lt;span class=&quot;plainlinks&quot;&gt;[{{filepath:CFD11_SST_Ahmed_25_y=195.dat}} y=195]&lt;/span&gt;;<br /> &lt;span class=&quot;plainlinks&quot;&gt;[{{filepath:CFD11_SST_Ahmed_25_z=360.dat}} z=360]&lt;/span&gt;<br /> <br /> &lt;span class=&quot;plainlinks&quot;&gt;[{{filepath:CFD11_SST_Ahmed_25_x=-794.dat}} x=-794]&lt;/span&gt;;<br /> &lt;span class=&quot;plainlinks&quot;&gt;[{{filepath:CFD11_SST_Ahmed_25_x=-178.dat}} x=-178]&lt;/span&gt;;<br /> &lt;span class=&quot;plainlinks&quot;&gt;[{{filepath:CFD11_SST_Ahmed_25_x=-138.dat}} x=-138]&lt;/span&gt;;<br /> &lt;span class=&quot;plainlinks&quot;&gt;[{{filepath:CFD11_SST_Ahmed_25_x=-88.dat}} x=-88]&lt;/span&gt;;<br /> &lt;span class=&quot;plainlinks&quot;&gt;[{{filepath:CFD11_SST_Ahmed_25_x=-38.dat}} x=-38]&lt;/span&gt;;<br /> &lt;span class=&quot;plainlinks&quot;&gt;[{{filepath:CFD11_SST_Ahmed_25_x=0.dat}} x=0]&lt;/span&gt;;<br /> &lt;span class=&quot;plainlinks&quot;&gt;[{{filepath:CFD11_SST_Ahmed_25_x=80.dat}} x=80]&lt;/span&gt;;<br /> &lt;span class=&quot;plainlinks&quot;&gt;[{{filepath:CFD11_SST_Ahmed_25_x=200.dat}} x=200]&lt;/span&gt;;<br /> &lt;span class=&quot;plainlinks&quot;&gt;[{{filepath:CFD11_SST_Ahmed_25_x=500.dat}} x=500]&lt;/span&gt;<br /> <br /> profiles in the boundary layer:<br /> &lt;span class=&quot;plainlinks&quot;&gt;[{{filepath:CFD11_SST_Ahmed_25_BL_x=-243.dat}} x=-243]&lt;/span&gt;,<br /> &lt;span class=&quot;plainlinks&quot;&gt;[{{filepath:CFD11_SST_Ahmed_25_BL_x=-223.dat}} -223]&lt;/span&gt;,<br /> &lt;span class=&quot;plainlinks&quot;&gt;[{{filepath:CFD11_SST_Ahmed_25_BL_x=-203.dat}} -203]&lt;/span&gt;,<br /> &lt;span class=&quot;plainlinks&quot;&gt;[{{filepath:CFD11_SST_Ahmed_25_BL_x=-183.dat}} -183]&lt;/span&gt;,<br /> &lt;span class=&quot;plainlinks&quot;&gt;[{{filepath:CFD11_SST_Ahmed_25_BL_x=-163.dat}} -163]&lt;/span&gt;,<br /> &lt;span class=&quot;plainlinks&quot;&gt;[{{filepath:CFD11_SST_Ahmed_25_BL_x=-143.dat}} -143]&lt;/span&gt;,<br /> &lt;span class=&quot;plainlinks&quot;&gt;[{{filepath:CFD11_SST_Ahmed_25_BL_x=-123.dat}} -123]&lt;/span&gt;,<br /> -103,<br /> &lt;span class=&quot;plainlinks&quot;&gt;[{{filepath:CFD11_SST_Ahmed_25_BL_x=-83.dat}} -83]&lt;/span&gt;,<br /> &lt;span class=&quot;plainlinks&quot;&gt;[{{filepath:CFD11_SST_Ahmed_25_BL_x=-63.dat}} -63]&lt;/span&gt;,<br /> &lt;span class=&quot;plainlinks&quot;&gt;[{{filepath:CFD11_SST_Ahmed_25_BL_x=-43.dat}} -43]&lt;/span&gt;,<br /> &lt;span class=&quot;plainlinks&quot;&gt;[{{filepath:CFD11_SST_Ahmed_25_BL_x=-23.dat}} -23]&lt;/span&gt;,<br /> &lt;span class=&quot;plainlinks&quot;&gt;[{{filepath:CFD11_SST_Ahmed_25_BL_x=-3.dat}} -3]&lt;/span&gt;<br /> <br /> Pressure coefficients on the rear of the body:<br /> &lt;span class=&quot;plainlinks&quot;&gt;[{{filepath:CFD11_SST_Ahmed_25_Cp.dat}} Cp]&lt;/span&gt;<br /> <br /> <br /> <br /> 35° slant angle:<br /> planes:<br /> &lt;span class=&quot;plainlinks&quot;&gt;[{{filepath:CFD11_SST_Ahmed_35_y=0.dat}} y=0]&lt;/span&gt;;<br /> &lt;span class=&quot;plainlinks&quot;&gt;[{{filepath:CFD11_SST_Ahmed_35_y=100.dat}} y=100]&lt;/span&gt;; <br /> &lt;span class=&quot;plainlinks&quot;&gt;[{{filepath:CFD11_SST_Ahmed_35_y=180.dat}} y=180]&lt;/span&gt;;<br /> <br /> &lt;span class=&quot;plainlinks&quot;&gt;[{{filepath:CFD11_SST_Ahmed_35_y=195.dat}} y=195]&lt;/span&gt;;<br /> z=360<br /> <br /> &lt;span class=&quot;plainlinks&quot;&gt;[{{filepath:CFD11_SST_Ahmed_35_x=-178.dat}} x=-178]&lt;/span&gt;;<br /> &lt;span class=&quot;plainlinks&quot;&gt;[{{filepath:CFD11_SST_Ahmed_35_x=-138.dat}} x=-138]&lt;/span&gt;;<br /> &lt;span class=&quot;plainlinks&quot;&gt;[{{filepath:CFD11_SST_Ahmed_35_x=-88.dat}} x=-88]&lt;/span&gt;;<br /> &lt;span class=&quot;plainlinks&quot;&gt;[{{filepath:CFD11_SST_Ahmed_35_x=-38.dat}} x=-38]&lt;/span&gt;;<br /> &lt;span class=&quot;plainlinks&quot;&gt;[{{filepath:CFD11_SST_Ahmed_35_x=0.dat}} x=0]&lt;/span&gt;;<br /> &lt;span class=&quot;plainlinks&quot;&gt;[{{filepath:CFD11_SST_Ahmed_35_x=80.dat}} x=80]&lt;/span&gt;;<br /> &lt;span class=&quot;plainlinks&quot;&gt;[{{filepath:CFD11_SST_Ahmed_35_x=200.dat}} x=200]&lt;/span&gt;;<br /> &lt;span class=&quot;plainlinks&quot;&gt;[{{filepath:CFD11_SST_Ahmed_35_x=500.dat}} x=500]&lt;/span&gt;<br /> <br /> profiles in the boundary layer:<br /> &lt;span class=&quot;plainlinks&quot;&gt;[{{filepath:CFD11_SST_Ahmed_35_BL_x=-243.dat}} x=-243]&lt;/span&gt;,<br /> &lt;span class=&quot;plainlinks&quot;&gt;[{{filepath:CFD11_SST_Ahmed_35_BL_x=-223.dat}} -223]&lt;/span&gt;,<br /> &lt;span class=&quot;plainlinks&quot;&gt;[{{filepath:CFD11_SST_Ahmed_35_BL_x=-203.dat}} -203]&lt;/span&gt;,<br /> &lt;span class=&quot;plainlinks&quot;&gt;[{{filepath:CFD11_SST_Ahmed_35_BL_x=-183.dat}} -183]&lt;/span&gt;,<br /> &lt;span class=&quot;plainlinks&quot;&gt;[{{filepath:CFD11_SST_Ahmed_35_BL_x=-163.dat}} -163]&lt;/span&gt;,<br /> &lt;span class=&quot;plainlinks&quot;&gt;[{{filepath:CFD11_SST_Ahmed_35_BL_x=-143.dat}} -143]&lt;/span&gt;,<br /> &lt;span class=&quot;plainlinks&quot;&gt;[{{filepath:CFD11_SST_Ahmed_35_BL_x=-123.dat}} -123]&lt;/span&gt;,<br /> &lt;span class=&quot;plainlinks&quot;&gt;[{{filepath:CFD11_SST_Ahmed_35_BL_x=-103.dat}} -103]&lt;/span&gt;,<br /> &lt;span class=&quot;plainlinks&quot;&gt;[{{filepath:CFD11_SST_Ahmed_35_BL_x=-83.dat}} -83]&lt;/span&gt;,<br /> &lt;span class=&quot;plainlinks&quot;&gt;[{{filepath:CFD11_SST_Ahmed_35_BL_x=-63.dat}} -63]&lt;/span&gt;,<br /> &lt;span class=&quot;plainlinks&quot;&gt;[{{filepath:CFD11_SST_Ahmed_35_BL_x=-43.dat}} -43]&lt;/span&gt;,<br /> &lt;span class=&quot;plainlinks&quot;&gt;[{{filepath:CFD11_SST_Ahmed_35_BL_x=-23.dat}} -23]&lt;/span&gt;,<br /> &lt;span class=&quot;plainlinks&quot;&gt;[{{filepath:CFD11_SST_Ahmed_35_BL_x=-3.dat}} -3]&lt;/span&gt;<br /> <br /> Pressure coefficients on the rear of the body:<br /> &lt;span class=&quot;plainlinks&quot;&gt;[{{filepath:CFD11_SST_Ahmed_35_Cp.dat}} Cp]&lt;/span&gt;<br /> <br /> =='''References CFD11'''==<br /> <br /> L. Durand, M. Kuntz, F. Menter, Validation of CFX-5 for the Ahmed car body (synopsis), in: R. Manceau, J.-P. Bonnet, editors, 10th ERCOFTAC (SIG-15)/IAHR/QNET-CFD Workshop on Refined Turbulence Modelling, Oct. 10-11, 2002, Laboratoire d’études aérodynamiques, UMR CNRS 6609, Université de Poitiers, France.<br /> <br /> <br /> <br /> L. Durand, M. Kuntz, F. Menter, Validation of CFX-5 for the Ahmed car body, CFX Validation report (florian.menter@ansys.com)<br /> <br /> <br /> =='''Simulation Case CFD12'''==<br /> <br /> ==='''Solution strategy CFD12'''===<br /> <br /> RANS modelling.<br /> <br /> In-house code CFL3D, compressible flow solver employing multi block structured grids. An upwind finite volume formulation is used for the space discretization. An implicit approximate factorization method is used to integrate the equations in time. Local time stepping, grid sequencing, multi grid and low Mach number preconditioning are used to accelerate convergence to steady state.<br /> <br /> Reynolds number: 2.78x106 (see EXP2). Steady state computation.<br /> <br /> Slant angle: 25° and 35°.<br /> <br /> ==='''Computational Domain CFD12'''===<br /> <br /> Symmetry is used to compute half the domain. No stilts included.<br /> <br /> Domain: [-3L;6L]x[0;0.9L]x[0;1.15L]<br /> <br /> Mesh : 1.3x106 cells<br /> <br /> Approximate value of y+ on solid surfaces : 1.5<br /> <br /> ==='''Boundary Conditions CFD12'''===<br /> <br /> Inlet: no details<br /> <br /> Solid boundaries: no-slip walls<br /> <br /> Symmetry plane: symmetry<br /> <br /> Other boundaries: farfield Riemann-invariant conditions<br /> <br /> ==='''Application of Physical Models CFD12'''===<br /> <br /> - SST model<br /> <br /> - Explicit Algebraic Stress Model with ω-equation<br /> <br /> ==='''Numerical Accuracy CFD12'''===<br /> <br /> Convection scheme : 1st order.<br /> <br /> ==='''CFD Results CFD12'''===<br /> <br /> The same quantities (except for triple correlations) as for experiment EXP2 are available in the Knowledge Base : results for the mean velocities U, V, W, Reynolds stresses [[Image:Image23.gif]] [[Image:Image24.gif]] [[Image:Image25.gif]] [[Image:Image26.gif]] [[Image:Image27.gif]] in some planes and profiles in the boundary layer above the slant part:<br /> <br /> <br /> <br /> '''SST model'''<br /> <br /> 25° slant angle:<br /> <br /> planes:<br /> &lt;span class=&quot;plainlinks&quot;&gt;[{{filepath:CFD12_SST_Ahmed_25_y=0.dat}} y=0]&lt;/span&gt;;<br /> &lt;span class=&quot;plainlinks&quot;&gt;[{{filepath:CFD12_SST_Ahmed_25_y=100.dat}} y=100]&lt;/span&gt;; <br /> &lt;span class=&quot;plainlinks&quot;&gt;[{{filepath:CFD12_SST_Ahmed_25_y=180.dat}} y=180]&lt;/span&gt;;<br /> <br /> &lt;span class=&quot;plainlinks&quot;&gt;[{{filepath:CFD12_SST_Ahmed_25_y=195.dat}} y=195]&lt;/span&gt;;<br /> &lt;span class=&quot;plainlinks&quot;&gt;[{{filepath:CFD12_SST_Ahmed_25_z=360.dat}} z=360]&lt;/span&gt;<br /> <br /> &lt;span class=&quot;plainlinks&quot;&gt;[{{filepath:CFD12_SST_Ahmed_25_x=-794.dat}} x=-794]&lt;/span&gt;;<br /> &lt;span class=&quot;plainlinks&quot;&gt;[{{filepath:CFD12_SST_Ahmed_25_x=-178.dat}} x=-178]&lt;/span&gt;;<br /> &lt;span class=&quot;plainlinks&quot;&gt;[{{filepath:CFD12_SST_Ahmed_25_x=-138.dat}} x=-138]&lt;/span&gt;;<br /> &lt;span class=&quot;plainlinks&quot;&gt;[{{filepath:CFD12_SST_Ahmed_25_x=-88.dat}} x=-88]&lt;/span&gt;;<br /> &lt;span class=&quot;plainlinks&quot;&gt;[{{filepath:CFD12_SST_Ahmed_25_x=-38.dat}} x=-38]&lt;/span&gt;;<br /> &lt;span class=&quot;plainlinks&quot;&gt;[{{filepath:CFD12_SST_Ahmed_25_x=0.dat}} x=0]&lt;/span&gt;;<br /> &lt;span class=&quot;plainlinks&quot;&gt;[{{filepath:CFD12_SST_Ahmed_25_x=80.dat}} x=80]&lt;/span&gt;;<br /> &lt;span class=&quot;plainlinks&quot;&gt;[{{filepath:CFD12_SST_Ahmed_25_x=200.dat}} x=200]&lt;/span&gt;;<br /> &lt;span class=&quot;plainlinks&quot;&gt;[{{filepath:CFD12_SST_Ahmed_25_x=500.dat}} x=500]&lt;/span&gt;<br /> <br /> profiles in the boundary layer:<br /> &lt;span class=&quot;plainlinks&quot;&gt;[{{filepath:CFD12_SST_Ahmed_25_BL_x=-243.dat}} x=-243]&lt;/span&gt;,<br /> &lt;span class=&quot;plainlinks&quot;&gt;[{{filepath:CFD12_SST_Ahmed_25_BL_x=-223.dat}} -223]&lt;/span&gt;,<br /> &lt;span class=&quot;plainlinks&quot;&gt;[{{filepath:CFD12_SST_Ahmed_25_BL_x=-203.dat}} -203]&lt;/span&gt;,<br /> &lt;span class=&quot;plainlinks&quot;&gt;[{{filepath:CFD12_SST_Ahmed_25_BL_x=-183.dat}} -183]&lt;/span&gt;,<br /> &lt;span class=&quot;plainlinks&quot;&gt;[{{filepath:CFD12_SST_Ahmed_25_BL_x=-163.dat}} -163]&lt;/span&gt;,<br /> &lt;span class=&quot;plainlinks&quot;&gt;[{{filepath:CFD12_SST_Ahmed_25_BL_x=-143.dat}} -143]&lt;/span&gt;,<br /> &lt;span class=&quot;plainlinks&quot;&gt;[{{filepath:CFD12_SST_Ahmed_25_BL_x=-123.dat}} -123]&lt;/span&gt;,<br /> &lt;span class=&quot;plainlinks&quot;&gt;[{{filepath:CFD12_SST_Ahmed_25_BL_x=-103.dat}} -103]&lt;/span&gt;,<br /> &lt;span class=&quot;plainlinks&quot;&gt;[{{filepath:CFD12_SST_Ahmed_25_BL_x=-83.dat}} -83]&lt;/span&gt;,<br /> &lt;span class=&quot;plainlinks&quot;&gt;[{{filepath:CFD12_SST_Ahmed_25_BL_x=-63.dat}} -63]&lt;/span&gt;,<br /> &lt;span class=&quot;plainlinks&quot;&gt;[{{filepath:CFD12_SST_Ahmed_25_BL_x=-43.dat}} -43]&lt;/span&gt;,<br /> &lt;span class=&quot;plainlinks&quot;&gt;[{{filepath:CFD12_SST_Ahmed_25_BL_x=-23.dat}} -23]&lt;/span&gt;,<br /> &lt;span class=&quot;plainlinks&quot;&gt;[{{filepath:CFD12_SST_Ahmed_25_BL_x=-3.dat}} -3]&lt;/span&gt;<br /> <br /> Pressure coefficients on the rear of the body:<br /> &lt;span class=&quot;plainlinks&quot;&gt;[{{filepath:CFD12_SST_Ahmed_25_Cp.dat}} Cp]&lt;/span&gt;<br /> <br /> <br /> 35° slant angle:<br /> <br /> planes:<br /> &lt;span class=&quot;plainlinks&quot;&gt;[{{filepath:CFD12_SST_Ahmed_35_y=0.dat}} y=0]&lt;/span&gt;;<br /> &lt;span class=&quot;plainlinks&quot;&gt;[{{filepath:CFD12_SST_Ahmed_35_y=100.dat}} y=100]&lt;/span&gt;; <br /> &lt;span class=&quot;plainlinks&quot;&gt;[{{filepath:CFD12_SST_Ahmed_35_y=180.dat}} y=180]&lt;/span&gt;;<br /> <br /> &lt;span class=&quot;plainlinks&quot;&gt;[{{filepath:CFD12_SST_Ahmed_35_y=195.dat}} y=195]&lt;/span&gt;;<br /> &lt;span class=&quot;plainlinks&quot;&gt;[{{filepath:CFD12_SST_Ahmed_35_z=360.dat}} z=360]&lt;/span&gt;<br /> <br /> &lt;span class=&quot;plainlinks&quot;&gt;[{{filepath:CFD12_SST_Ahmed_35_x=-794.dat}} x=-794]&lt;/span&gt;;<br /> &lt;span class=&quot;plainlinks&quot;&gt;[{{filepath:CFD12_SST_Ahmed_35_x=-178.dat}} x=-178]&lt;/span&gt;;<br /> &lt;span class=&quot;plainlinks&quot;&gt;[{{filepath:CFD12_SST_Ahmed_35_x=-138.dat}} x=-138]&lt;/span&gt;;<br /> &lt;span class=&quot;plainlinks&quot;&gt;[{{filepath:CFD12_SST_Ahmed_35_x=-88.dat}} x=-88]&lt;/span&gt;;<br /> &lt;span class=&quot;plainlinks&quot;&gt;[{{filepath:CFD12_SST_Ahmed_35_x=-38.dat}} x=-38]&lt;/span&gt;;<br /> &lt;span class=&quot;plainlinks&quot;&gt;[{{filepath:CFD12_SST_Ahmed_35_x=0.dat}} x=0]&lt;/span&gt;;<br /> &lt;span class=&quot;plainlinks&quot;&gt;[{{filepath:CFD12_SST_Ahmed_35_x=80.dat}} x=80]&lt;/span&gt;;<br /> &lt;span class=&quot;plainlinks&quot;&gt;[{{filepath:CFD12_SST_Ahmed_35_x=200.dat}} x=200]&lt;/span&gt;;<br /> &lt;span class=&quot;plainlinks&quot;&gt;[{{filepath:CFD12_SST_Ahmed_35_x=500.dat}} x=500]&lt;/span&gt;<br /> <br /> profiles in the boundary layer:<br /> &lt;span class=&quot;plainlinks&quot;&gt;[{{filepath:CFD12_SST_Ahmed_35_BL_x=-243.dat}} x=-243]&lt;/span&gt;,<br /> &lt;span class=&quot;plainlinks&quot;&gt;[{{filepath:CFD12_SST_Ahmed_35_BL_x=-223.dat}} -223]&lt;/span&gt;,<br /> &lt;span class=&quot;plainlinks&quot;&gt;[{{filepath:CFD12_SST_Ahmed_35_BL_x=-203.dat}} -203]&lt;/span&gt;,<br /> &lt;span class=&quot;plainlinks&quot;&gt;[{{filepath:CFD12_SST_Ahmed_35_BL_x=-183.dat}} -183]&lt;/span&gt;,<br /> &lt;span class=&quot;plainlinks&quot;&gt;[{{filepath:CFD12_SST_Ahmed_35_BL_x=-163.dat}} -163]&lt;/span&gt;,<br /> &lt;span class=&quot;plainlinks&quot;&gt;[{{filepath:CFD12_SST_Ahmed_35_BL_x=-143.dat}} -143]&lt;/span&gt;,<br /> &lt;span class=&quot;plainlinks&quot;&gt;[{{filepath:CFD12_SST_Ahmed_35_BL_x=-123.dat}} -123]&lt;/span&gt;,<br /> &lt;span class=&quot;plainlinks&quot;&gt;[{{filepath:CFD12_SST_Ahmed_35_BL_x=-103.dat}} -103]&lt;/span&gt;,<br /> &lt;span class=&quot;plainlinks&quot;&gt;[{{filepath:CFD12_SST_Ahmed_35_BL_x=-83.dat}} -83]&lt;/span&gt;,<br /> &lt;span class=&quot;plainlinks&quot;&gt;[{{filepath:CFD12_SST_Ahmed_35_BL_x=-63.dat}} -63]&lt;/span&gt;,<br /> &lt;span class=&quot;plainlinks&quot;&gt;[{{filepath:CFD12_SST_Ahmed_35_BL_x=-43.dat}} -43]&lt;/span&gt;,<br /> &lt;span class=&quot;plainlinks&quot;&gt;[{{filepath:CFD12_SST_Ahmed_35_BL_x=-23.dat}} -23]&lt;/span&gt;,<br /> &lt;span class=&quot;plainlinks&quot;&gt;[{{filepath:CFD12_SST_Ahmed_35_BL_x=-3.dat}} -3]&lt;/span&gt;<br /> <br /> Pressure coefficients on the rear of the body:<br /> &lt;span class=&quot;plainlinks&quot;&gt;[{{filepath:CFD12_SST_Ahmed_35_Cp.dat}} Cp]&lt;/span&gt;<br /> <br /> <br /> <br /> '''EASM model'''<br /> <br /> 25° slant angle:<br /> <br /> planes:<br /> &lt;span class=&quot;plainlinks&quot;&gt;[{{filepath:CFD12_EASM_Ahmed_25_y=0.dat}} y=0]&lt;/span&gt;;<br /> &lt;span class=&quot;plainlinks&quot;&gt;[{{filepath:CFD12_EASM_Ahmed_25_y=100.dat}} y=100]&lt;/span&gt;; <br /> &lt;span class=&quot;plainlinks&quot;&gt;[{{filepath:CFD12_EASM_Ahmed_25_y=180.dat}} y=180]&lt;/span&gt;;<br /> <br /> &lt;span class=&quot;plainlinks&quot;&gt;[{{filepath:CFD12_EASM_Ahmed_25_y=195.dat}} y=195]&lt;/span&gt;;<br /> &lt;span class=&quot;plainlinks&quot;&gt;[{{filepath:CFD12_EASM_Ahmed_25_z=360.dat}} z=360]&lt;/span&gt;<br /> <br /> &lt;span class=&quot;plainlinks&quot;&gt;[{{filepath:CFD12_EASM_Ahmed_25_x=-794.dat}} x=-794]&lt;/span&gt;;<br /> &lt;span class=&quot;plainlinks&quot;&gt;[{{filepath:CFD12_EASM_Ahmed_25_x=-178.dat}} x=-178]&lt;/span&gt;;<br /> &lt;span class=&quot;plainlinks&quot;&gt;[{{filepath:CFD12_EASM_Ahmed_25_x=-138.dat}} x=-138]&lt;/span&gt;;<br /> &lt;span class=&quot;plainlinks&quot;&gt;[{{filepath:CFD12_EASM_Ahmed_25_x=-88.dat}} x=-88]&lt;/span&gt;;<br /> &lt;span class=&quot;plainlinks&quot;&gt;[{{filepath:CFD12_EASM_Ahmed_25_x=-38.dat}} x=-38]&lt;/span&gt;;<br /> &lt;span class=&quot;plainlinks&quot;&gt;[{{filepath:CFD12_EASM_Ahmed_25_x=0.dat}} x=0]&lt;/span&gt;;<br /> &lt;span class=&quot;plainlinks&quot;&gt;[{{filepath:CFD12_EASM_Ahmed_25_x=80.dat}} x=80]&lt;/span&gt;;<br /> &lt;span class=&quot;plainlinks&quot;&gt;[{{filepath:CFD12_EASM_Ahmed_25_x=200.dat}} x=200]&lt;/span&gt;;<br /> &lt;span class=&quot;plainlinks&quot;&gt;[{{filepath:CFD12_EASM_Ahmed_25_x=500.dat}} x=500]&lt;/span&gt;<br /> <br /> profiles in the boundary layer:<br /> &lt;span class=&quot;plainlinks&quot;&gt;[{{filepath:CFD12_EASM_Ahmed_25_BL_x=-243.dat}} x=-243]&lt;/span&gt;,<br /> &lt;span class=&quot;plainlinks&quot;&gt;[{{filepath:CFD12_EASM_Ahmed_25_BL_x=-223.dat}} -223]&lt;/span&gt;,<br /> &lt;span class=&quot;plainlinks&quot;&gt;[{{filepath:CFD12_EASM_Ahmed_25_BL_x=-203.dat}} -203]&lt;/span&gt;,<br /> &lt;span class=&quot;plainlinks&quot;&gt;[{{filepath:CFD12_EASM_Ahmed_25_BL_x=-183.dat}} -183]&lt;/span&gt;,<br /> &lt;span class=&quot;plainlinks&quot;&gt;[{{filepath:CFD12_EASM_Ahmed_25_BL_x=-163.dat}} -163]&lt;/span&gt;,<br /> &lt;span class=&quot;plainlinks&quot;&gt;[{{filepath:CFD12_EASM_Ahmed_25_BL_x=-143.dat}} -143]&lt;/span&gt;,<br /> &lt;span class=&quot;plainlinks&quot;&gt;[{{filepath:CFD12_EASM_Ahmed_25_BL_x=-123.dat}} -123]&lt;/span&gt;,<br /> &lt;span class=&quot;plainlinks&quot;&gt;[{{filepath:CFD12_EASM_Ahmed_25_BL_x=-103.dat}} -103]&lt;/span&gt;,<br /> &lt;span class=&quot;plainlinks&quot;&gt;[{{filepath:CFD12_EASM_Ahmed_25_BL_x=-83.dat}} -83]&lt;/span&gt;,<br /> &lt;span class=&quot;plainlinks&quot;&gt;[{{filepath:CFD12_EASM_Ahmed_25_BL_x=-63.dat}} -63]&lt;/span&gt;,<br /> &lt;span class=&quot;plainlinks&quot;&gt;[{{filepath:CFD12_EASM_Ahmed_25_BL_x=-43.dat}} -43]&lt;/span&gt;,<br /> &lt;span class=&quot;plainlinks&quot;&gt;[{{filepath:CFD12_EASM_Ahmed_25_BL_x=-23.dat}} -23]&lt;/span&gt;,<br /> &lt;span class=&quot;plainlinks&quot;&gt;[{{filepath:CFD12_EASM_Ahmed_25_BL_x=-3.dat}} -3]&lt;/span&gt;<br /> <br /> Pressure coefficients on the rear of the body:<br /> &lt;span class=&quot;plainlinks&quot;&gt;[{{filepath:CFD12_EASM_Ahmed_25_Cp.dat}} Cp]&lt;/span&gt;<br /> <br /> <br /> 35° slant angle:<br /> <br /> planes:<br /> &lt;span class=&quot;plainlinks&quot;&gt;[{{filepath:CFD12_EASM_Ahmed_35_y=0.dat}} y=0]&lt;/span&gt;;<br /> &lt;span class=&quot;plainlinks&quot;&gt;[{{filepath:CFD12_EASM_Ahmed_35_y=100.dat}} y=100]&lt;/span&gt;; <br /> &lt;span class=&quot;plainlinks&quot;&gt;[{{filepath:CFD12_EASM_Ahmed_35_y=180.dat}} y=180]&lt;/span&gt;;<br /> <br /> &lt;span class=&quot;plainlinks&quot;&gt;[{{filepath:CFD12_EASM_Ahmed_35_y=195.dat}} y=195]&lt;/span&gt;;<br /> &lt;span class=&quot;plainlinks&quot;&gt;[{{filepath:CFD12_EASM_Ahmed_35_z=360.dat}} z=360]&lt;/span&gt;<br /> <br /> &lt;span class=&quot;plainlinks&quot;&gt;[{{filepath:CFD12_EASM_Ahmed_35_x=-794.dat}} x=-794]&lt;/span&gt;;<br /> &lt;span class=&quot;plainlinks&quot;&gt;[{{filepath:CFD12_EASM_Ahmed_35_x=-178.dat}} x=-178]&lt;/span&gt;;<br /> &lt;span class=&quot;plainlinks&quot;&gt;[{{filepath:CFD12_EASM_Ahmed_35_x=-138.dat}} x=-138]&lt;/span&gt;;<br /> &lt;span class=&quot;plainlinks&quot;&gt;[{{filepath:CFD12_EASM_Ahmed_35_x=-88.dat}} x=-88]&lt;/span&gt;;<br /> &lt;span class=&quot;plainlinks&quot;&gt;[{{filepath:CFD12_EASM_Ahmed_35_x=-38.dat}} x=-38]&lt;/span&gt;;<br /> &lt;span class=&quot;plainlinks&quot;&gt;[{{filepath:CFD12_EASM_Ahmed_35_x=0.dat}} x=0]&lt;/span&gt;;<br /> &lt;span class=&quot;plainlinks&quot;&gt;[{{filepath:CFD12_EASM_Ahmed_35_x=80.dat}} x=80]&lt;/span&gt;;<br /> &lt;span class=&quot;plainlinks&quot;&gt;[{{filepath:CFD12_EASM_Ahmed_35_x=200.dat}} x=200]&lt;/span&gt;;<br /> &lt;span class=&quot;plainlinks&quot;&gt;[{{filepath:CFD12_EASM_Ahmed_35_x=500.dat}} x=500]&lt;/span&gt;<br /> <br /> profiles in the boundary layer:<br /> &lt;span class=&quot;plainlinks&quot;&gt;[{{filepath:CFD12_EASM_Ahmed_35_BL_x=-243.dat}} x=-243]&lt;/span&gt;,<br /> &lt;span class=&quot;plainlinks&quot;&gt;[{{filepath:CFD12_EASM_Ahmed_35_BL_x=-223.dat}} -223]&lt;/span&gt;,<br /> &lt;span class=&quot;plainlinks&quot;&gt;[{{filepath:CFD12_EASM_Ahmed_35_BL_x=-203.dat}} -203]&lt;/span&gt;,<br /> &lt;span class=&quot;plainlinks&quot;&gt;[{{filepath:CFD12_EASM_Ahmed_35_BL_x=-183.dat}} -183]&lt;/span&gt;,<br /> &lt;span class=&quot;plainlinks&quot;&gt;[{{filepath:CFD12_EASM_Ahmed_35_BL_x=-163.dat}} -163]&lt;/span&gt;,<br /> &lt;span class=&quot;plainlinks&quot;&gt;[{{filepath:CFD12_EASM_Ahmed_35_BL_x=-143.dat}} -143]&lt;/span&gt;,<br /> &lt;span class=&quot;plainlinks&quot;&gt;[{{filepath:CFD12_EASM_Ahmed_35_BL_x=-123.dat}} -123]&lt;/span&gt;,<br /> &lt;span class=&quot;plainlinks&quot;&gt;[{{filepath:CFD12_EASM_Ahmed_35_BL_x=-103.dat}} -103]&lt;/span&gt;,<br /> &lt;span class=&quot;plainlinks&quot;&gt;[{{filepath:CFD12_EASM_Ahmed_35_BL_x=-83.dat}} -83]&lt;/span&gt;,<br /> &lt;span class=&quot;plainlinks&quot;&gt;[{{filepath:CFD12_EASM_Ahmed_35_BL_x=-63.dat}} -63]&lt;/span&gt;,<br /> &lt;span class=&quot;plainlinks&quot;&gt;[{{filepath:CFD12_EASM_Ahmed_35_BL_x=-43.dat}} -43]&lt;/span&gt;,<br /> &lt;span class=&quot;plainlinks&quot;&gt;[{{filepath:CFD12_EASM_Ahmed_35_BL_x=-23.dat}} -23]&lt;/span&gt;,<br /> &lt;span class=&quot;plainlinks&quot;&gt;[{{filepath:CFD12_EASM_Ahmed_35_BL_x=-3.dat}} -3]&lt;/span&gt;<br /> <br /> Pressure coefficients on the rear of the body:<br /> &lt;span class=&quot;plainlinks&quot;&gt;[{{filepath:CFD12_EASM_Ahmed_35_Cp.dat}} Cp]&lt;/span&gt;<br /> <br /> =='''References CFD12'''==<br /> <br /> C.L. Rumsey, Application of CFL3D to case 9.4 (Ahmed Body), in: R. Manceau, J.-P. Bonnet, editors, 10th ERCOFTAC (SIG-15)/IAHR/QNET-CFD Workshop on Refined Turbulence Modelling, Oct. 10-11, 2002, Laboratoire d’études aérodynamiques, UMR CNRS 6609, Université de Poitiers, France.<br /> <br /> <br /> =='''Simulation Case CFD13'''==<br /> <br /> ==='''Solution strategy CFD13'''===<br /> <br /> RANS modelling.<br /> <br /> In-house code STREAM, which is a finite volume solver which uses a structured, non-orthogonal curvilinear, multi block grid and a fully collocated arrangement. The SIMPLE pressure correction method and Rie &amp; Chow interpolation are used to prevent unrealistic pressure fluctuations. The convection terms are discretized using an upwind scheme or a TVD scheme based on the third-order QUICK scheme<br /> <br /> Reynolds number: 2.78x106 (see EXP2). Steady state computation.<br /> <br /> Slant angle: 25°.<br /> <br /> ==='''Computational Domain CFD13'''===<br /> <br /> Symmetry is used to compute half the domain. No stilts included.<br /> <br /> Domain: [-3L;6L]x[0;0.9L]x[0;1.15L]<br /> <br /> Mesh : 1.3x106 cells<br /> <br /> Approximate value of y+ on solid surfaces : 1<br /> <br /> ==='''Boundary Conditions CFD13'''===<br /> <br /> Inlet: no details<br /> <br /> Solid boundaries: no-slip walls<br /> <br /> Other boundaries: symmetry<br /> <br /> ===''''Application of Physical Models CFD13'''===<br /> <br /> All are low-Reynolds number models<br /> <br /> - Linear k-ε model (Launder-Sharma)<br /> <br /> - Linear k-ω model (Wilcox)<br /> <br /> - Cubic k-ε model (Apsley, Leschziner)<br /> <br /> - Quadratic k-ω model (Abe, Jang, Leschziner)<br /> <br /> - Quadratic k-ε model (Abe, Jang, Leschziner)<br /> <br /> - SSG + Chen (Abe, Jang, Leschziner)<br /> <br /> ==='''Numerical Accuracy CFD13'''===<br /> <br /> No details<br /> <br /> ==='''CFD Results CFD13'''===<br /> <br /> Cp contours on the slant part, velocity profiles in the boundary layer over the slant part, vectors plots in 13 planes (see EXP2).<br /> <br /> =='''References CFD13'''==<br /> '''Y.J. Jang, M. Leschziner, Contribution of Imperial College to Test Case 9.4: Flow around a simplified car body, In: R. Manceau, J.-P. Bonnet, editors, '''''10th ERCOFTAC (SIG-15)/IAHR/QNET-CFD Workshop on Refined Turbulence Modelling, Oct. 10-11, 2002, Laboratoire d’études aérodynamiques, UMR CNRS 6609, Université de Poitiers, France.'''''<br /> <br /> <br /> =='''Simulation Case CFD14'''==<br /> <br /> ==='''Solution strategy CFD14'''===<br /> <br /> RANS modelling.<br /> <br /> In-house code ISIS, based on unstructured finite volume discretization.<br /> <br /> Reynolds number: 2.78x106 (see EXP2). Steady state computation.<br /> <br /> Slant angle: 25° and 35°.<br /> <br /> ==='''Computational Domain CFD14'''===<br /> <br /> Symmetry is used to compute half the domain.<br /> <br /> Domain: [-4L;5L]x[0;0.9L]x[0;1.35L]<br /> <br /> Mesh : 3.8x106 cells<br /> <br /> Approximate value of y+ on solid surfaces: 0.5<br /> <br /> ==='''Boundary Conditions CFD14'''===<br /> <br /> Solid boundaries: no slip wall<br /> <br /> Symmetry plane: symmetry<br /> <br /> Other boundaries: no details<br /> <br /> ==='''Application of Physical Models CFD14'''===<br /> <br /> SST model<br /> <br /> ==='''Numerical Accuracy CFD14'''===<br /> <br /> No details<br /> <br /> ==='''CFD Results CFD14'''===<br /> <br /> Velocity profiles in the boundary layer over the slant part, streamlines, turbulent energy contours.<br /> <br /> =='''References CFD14'''==<br /> <br /> E. Guilmineau, Numerical simulation of flow around a simplified car body, Proc. ASME JSME Joint Fluids Engineering Conference, July 6-10, 2003, Honolulu, Hawaii, USA<br /> <br /> <br /> =='''Simulation Case CFD15'''==<br /> <br /> ==='''Solution strategy CFD15'''===<br /> <br /> RANS modelling.<br /> <br /> Commercial StarCD code, based on unstructured finite volume discretization.<br /> <br /> Reynolds number: 2.78x106 (see EXP2). Steady state computation.<br /> <br /> Slant angle: 25°.<br /> <br /> ==='''Computational Domain CFD15'''===<br /> <br /> Symmetry is used to compute half the domain. No stilts included. The ground plate starts 2L upstream of the body in order to reproduce the experimental boundary layer.<br /> <br /> Domain: [-5.75L;5.75L]x[0;L]x[0;1.35L]<br /> <br /> Mesh : 1.6x106 cells<br /> <br /> Approximate value of y+ on solid surfaces : &lt; 3<br /> <br /> ==='''Boundary Conditions CFD15'''===<br /> <br /> Inlet: turbulence level 0.1%, nt/n=10.<br /> <br /> Outlet: convective outlet.<br /> <br /> Solid boundaries: no-slip walls<br /> <br /> Symmetry plane: symmetry<br /> <br /> Other boundaries: symmetry<br /> <br /> ==='''Application of Physical Models CFD15'''===<br /> <br /> Rescaled V2F model (Manceau, Carlson, Gatski)<br /> <br /> ==='''Numerical Accuracy CFD15'''===<br /> <br /> No details.<br /> <br /> ==='''CFD Results CFD15'''===<br /> <br /> Vector plots.<br /> <br /> =='''References CFD15'''==<br /> <br /> R. Manceau, Computation of the flow around a simplified car using the rescaled v2f model, ''Proc. ASME JSME Joint Fluids Engineering Conference, July 6-10, 2003, Honolulu, Hawaii, USA''<br /> <br /> <br /> {| align=&quot;center&quot; width=&quot;700&quot; border=&quot;1&quot;<br /> |+ align=&quot;bottom&quot; | Table CFD-A Summary Description of CFD1 - CFD15 Test Cases<br /> ! NAME<br /> ! Re x 10&lt;sup&gt;-6&lt;/sup&gt;<br /> ! width=&quot;90&quot; | Slant angle (degrees)<br /> ! colspan=&quot;2&quot; | [[DOAPs#SPs:_Simulated_Parameters|SPs]]<br /> |-<br /> |<br /> |<br /> |<br /> ! width=&quot;80&quot; | Detailed Data<br /> ! [[DOAPs#DOAPs:_Design_or_Assessment_Parameters|DOAP]]<br /> |-<br /> ! align=&quot;left&quot; | CFD1<br /> | align=&quot;center&quot; | 4.29<br /> | align=&quot;center&quot; | 0, 10, 12, 20, 25, 30, 40, 50<br /> | align=&quot;center&quot; | Pressure&amp;nbsp;Tomographies<br /> | align=&quot;center&quot; | C&lt;sub&gt;d&lt;/sub&gt;, Streamlines, Friction&amp;nbsp;Lines<br /> |-<br /> ! align=&quot;left&quot; | CFD2<br /> | align=&quot;center&quot; | 4.29<br /> | align=&quot;center&quot; | 30<br /> | align=&quot;center&quot; | Effective&amp;nbsp;Viscosity<br /> | align=&quot;center&quot; | C&lt;sub&gt;D&lt;/sub&gt;, Velocities<br /> |-<br /> ! align=&quot;left&quot; | CFD3<br /> | align=&quot;center&quot; | 4.29<br /> | align=&quot;center&quot; | 28<br /> | align=&quot;center&quot; | Pressure&amp;nbsp;Coefficient, Q-criterion&amp;nbsp;Contours<br /> | align=&quot;center&quot; | C&lt;sub&gt;d&lt;/sub&gt;, Velocities, Vorticity&amp;nbsp;Contours<br /> |-<br /> ! align=&quot;left&quot; | CFD4<br /> | align=&quot;center&quot; | 2.78<br /> | align=&quot;center&quot; | 25, 35<br /> | align=&quot;center&quot; | C&lt;sub&gt;P&lt;/sub&gt;<br /> | align=&quot;center&quot; | Velocity&amp;nbsp;Profiles<br /> |-<br /> ! align=&quot;left&quot; | CFD5<br /> | align=&quot;center&quot; | 2.78<br /> | align=&quot;center&quot; | 25, 35<br /> | align=&quot;center&quot; | C&lt;sub&gt;P&lt;/sub&gt;, Turbulent&amp;nbsp;Energy&amp;nbsp;Contours<br /> | align=&quot;center&quot; | Velocity&amp;nbsp;Profiles, Vector&amp;nbsp;Plots, Streamlines<br /> |-<br /> ! align=&quot;left&quot; | CFD6<br /> | align=&quot;center&quot; | 2.78<br /> | align=&quot;center&quot; | 25<br /> | align=&quot;center&quot; | C&lt;sub&gt;P&lt;/sub&gt;<br /> | align=&quot;center&quot; | Velocity&amp;nbsp;Profiles<br /> |-<br /> ! align=&quot;left&quot; | CFD7<br /> | align=&quot;center&quot; | 2.78<br /> | align=&quot;center&quot; | 35<br /> | align=&quot;center&quot; | C&lt;sub&gt;P&lt;/sub&gt;<br /> | align=&quot;center&quot; | Velocity&amp;nbsp;Profiles, Vector&amp;nbsp;Plots<br /> |-<br /> ! align=&quot;left&quot; | CFD8<br /> | align=&quot;center&quot; | 2.78<br /> | align=&quot;center&quot; | 25, 35<br /> | align=&quot;center&quot; | C&lt;sub&gt;P&lt;/sub&gt;<br /> | align=&quot;center&quot; | Velocity&amp;nbsp;Profiles, Vector&amp;nbsp;Plots<br /> |-<br /> ! align=&quot;left&quot; | CFD9<br /> | align=&quot;center&quot; | 2.78<br /> | align=&quot;center&quot; | 25, 35<br /> | align=&quot;center&quot; | C&lt;sub&gt;P&lt;/sub&gt;<br /> | align=&quot;center&quot; | Velocity&amp;nbsp;Profiles, Vector&amp;nbsp;Plots<br /> |-<br /> ! align=&quot;left&quot; | CFD10<br /> | align=&quot;center&quot; | 2.78<br /> | align=&quot;center&quot; | 25<br /> | align=&quot;center&quot; | C&lt;sub&gt;P&lt;/sub&gt;<br /> | align=&quot;center&quot; | Velocity&amp;nbsp;Profiles, Vector&amp;nbsp;Plots<br /> |-<br /> ! align=&quot;left&quot; | CFD11<br /> | align=&quot;center&quot; | 2.78<br /> | align=&quot;center&quot; | 35<br /> | align=&quot;center&quot; | C&lt;sub&gt;P&lt;/sub&gt;<br /> | align=&quot;center&quot; | C&lt;sub&gt;d&lt;/sub&gt;, Velocity&amp;nbsp;Profiles, Vector&amp;nbsp;Plots<br /> |-<br /> ! align=&quot;left&quot; | CFD12<br /> | align=&quot;center&quot; | 2.78<br /> | align=&quot;center&quot; | 25, 35<br /> | align=&quot;center&quot; | C&lt;sub&gt;P&lt;/sub&gt;<br /> | align=&quot;center&quot; | Velocity&amp;nbsp;Profiles, Vector&amp;nbsp;Plots<br /> |-<br /> ! align=&quot;left&quot; | CFD13<br /> | align=&quot;center&quot; | 2.78<br /> | align=&quot;center&quot; | 25<br /> | align=&quot;center&quot; | C&lt;sub&gt;P&lt;/sub&gt;<br /> | align=&quot;center&quot; | Velocity&amp;nbsp;Profiles, Vector&amp;nbsp;Plots<br /> |-<br /> ! align=&quot;left&quot; | CFD14<br /> | align=&quot;center&quot; | 2.78<br /> | align=&quot;center&quot; | 25, 35<br /> | align=&quot;center&quot; | Turbulent&amp;nbsp;Energy&amp;nbsp;Contours<br /> | align=&quot;center&quot; | Velocity&amp;nbsp;Profiles, Streamlines<br /> |-<br /> ! align=&quot;left&quot; | CFD15<br /> | align=&quot;center&quot; | 2.78<br /> | align=&quot;center&quot; | 25<br /> |<br /> | align=&quot;center&quot; | Vector&amp;nbsp;Plots<br /> |}<br /> <br /> =='''Simulation Case CFD16 (added in 2024 by F.R. Menter)'''==<br /> <br /> ==='''Solution Strategy CFD16'''===<br /> <br /> Large Eddy Simulation – Several simulations using different wall treatments and different meshes. <br /> <br /> Commercial Fluent and Fluent-GPU codes<br /> <br /> Reynolds number 2.78e6 (EXP2) (also simulations for lower Re=0.72e6)<br /> <br /> Slant angle 25°<br /> <br /> ==='''Computational Domain CFD16'''===<br /> <br /> All geometry included.<br /> <br /> Domain [m] [-3,6] x [-3,3] x [0, 3.5]<br /> <br /> Meshes from 7e6 to 560e6. (given in reference)<br /> <br /> Y+ values varying for different meshes (wall-resolved to wall function meshes)<br /> <br /> ==='''Boundary Conditions CFD16'''===<br /> <br /> Inlet – Velocity constant<br /> <br /> Bottom wind tunnel wall: non-slip<br /> <br /> Other wind tunnel walls: Slip walls<br /> <br /> Outlet: Pressure outlet<br /> <br /> ==='''Application of Physical Models CFD16'''===<br /> <br /> (described in Fluent Manual A.F.U. R-22.1, 2022)<br /> <br /> WALE model<br /> <br /> Wall-Resolved LES<br /> <br /> Wall-Function LES<br /> <br /> ==='''Numerical Accuracy CFD16'''===<br /> <br /> 2nd order code<br /> <br /> Wide range of meshes (given in reference)<br /> <br /> ==='''CFD Results CFD16'''===<br /> <br /> Wall shear stress on the roof-center plane, velocity and streamwise fluctuation profiles on the slant, wall streamlines on the slant, turbulent structures around the car body.<br /> <br /> =='''References CFD16'''==<br /> <br /> Menter, F.R., Hüppe, A., Flad, D. et al. Large Eddy Simulations for the Ahmed Car at 25° Slant Angle at Different Reynolds Numbers. Flow Turbulence Combust 112, 321–343 (2024).<br /> <br /> <br /> <br /> <br /> © copyright ERCOFTAC 2004<br /> <br /> ----<br /> <br /> <br /> ''Contributors: Remi Manceau; Jean-Paul Bonnet - Université de Poitiers. &amp;mdash; Update (2024) F.R.Menter, ANSYS Germany '', <br /> <br /> Site Design and Implementation:[[Atkins]] and [[UniS]]<br /> <br /> {{AC|front=AC 1-05|description=Description_AC1-05|testdata=Test Data_AC1-05|cfdsimulations=CFD Simulations_AC1-05|evaluation=Evaluation_AC1-05|qualityreview=Quality Review_AC1-05|bestpractice=Best Practice Advice_AC1-05|relatedUFRs=Related UFRs_AC1-05}}</div> Mike https://kbwiki.ercoftac.org/w/index.php?title=Test_Data_AC1-05&diff=45212 Test Data AC1-05 2024-02-14T09:46:38Z <p>Mike: </p> <hr /> <div>{{AC|front=AC 1-05|description=Description_AC1-05|testdata=Test Data_AC1-05|cfdsimulations=CFD Simulations_AC1-05|evaluation=Evaluation_AC1-05|qualityreview=Quality Review_AC1-05|bestpractice=Best Practice Advice_AC1-05|relatedUFRs=Related UFRs_AC1-05}}<br /> <br /> ='''Ahmed body'''=<br /> <br /> '''Application Challenge 1-05''' © copyright ERCOFTAC 2004<br /> <br /> <br /> <br /> =='''Overview of Tests'''==<br /> <br /> The first experiment (Exp1) deals with conventional average values such as oil flow patterns, static pressure measured on large times. Thus no information about unsteadiness will be included in the data. In Exp1, conventional wake surveys are performed with 10 hole probes. Drag is measured by strain gauge balance. The contribution of the drag is estimated for each part of the model. (front, slant rear, vertical rear base). The Reynolds number based on the model total length is 4.29 x 10&lt;sup&gt;6&lt;/sup&gt;.<br /> <br /> The second experiment (Exp2) uses a two-components LDV system. Averages are performed on a high number of samples (40000) for long time durations, typically 5 minutes.<br /> <br /> <br /> {| border=&quot;1&quot; align=&quot;center&quot;<br /> |+ Table EXP-A Summary Description of All Test Cases<br /> ! align=&quot;center&quot; | NAME<br /> ! align=&quot;center&quot; | [[DOAPs#GNDPs:_Governing_Non-Dimensional_Parameters|GNDPs]]<br /> ! align=&quot;center&quot; colspan=&quot;3&quot; | [[DOAPs#PDPs:_Problem_Definition_Parameters|PDPs]]<br /> ! align=&quot;center&quot; colspan=&quot;2&quot; | [[DOAPs#MPs:_Measured_Parameters|MPs]]<br /> |-<br /> !<br /> ! align=&quot;center&quot; | Re<br /> ! align=&quot;center&quot; | External velocity<br /> ! align=&quot;center&quot; | External turbulence level<br /> ! align=&quot;center&quot; | Slant angle<br /> ! align=&quot;center&quot; | Detailed Data<br /> ! align=&quot;center&quot; | [[DOAPs#DOAPs:_Design_or_Assessment_Parameters|DOAPs]]<br /> |-<br /> | align=&quot;center&quot; | EXP 1 Ahmed original (1984)<br /> | align=&quot;center&quot; | 4.29x10&lt;sup&gt;6&lt;/sup&gt;<br /> | align=&quot;center&quot; | 60ms&lt;sup&gt;-1&lt;/sup&gt;<br /> | align=&quot;center&quot; | 0.5%<br /> | align=&quot;center&quot; | 5&amp;deg;, 12.5&amp;deg;, 25&amp;deg;, 30&amp;deg;<br /> | align=&quot;center&quot; | P&lt;sub&gt;w&lt;/sub&gt;, U&lt;sub&gt;i&lt;/sub&gt;<br /> | align=&quot;center&quot; | C&lt;sub&gt;x&lt;/sub&gt;, Flow structure<br /> |-<br /> !<br /> ! align=&quot;center&quot; | Re<br /> !<br /> !<br /> !<br /> ! align=&quot;center&quot; | Detailed Data<br /> ! align=&quot;center&quot; | [[DOAPs#DOAPs:_Design_or_Assessment_Parameters|DOAPs]]<br /> |-<br /> | align=&quot;center&quot; | EXP2 Lienhart et al. (2000)<br /> | align=&quot;center&quot; | 2.78x10&lt;sup&gt;6&lt;/sup&gt;<br /> | align=&quot;center&quot; | 40ms&lt;sup&gt;-1&lt;/sup&gt;<br /> | align=&quot;center&quot; | 0.25%<br /> | align=&quot;center&quot; | 25&amp;deg;, 35&amp;deg;<br /> | align=&quot;center&quot; | First, second and third moments<br /> | align=&quot;center&quot; | P&lt;sub&gt;w&lt;/sub&gt;, Flow structure<br /> |}<br /> <br /> =='''Test Case EXP-1'''==<br /> <br /> ==='''Description of Experiment'''===<br /> <br /> See table<br /> <br /> ==='''Boundary Data'''===<br /> <br /> '''The test section is a ¾ open test section. Only the floor is a solid boundary. The homogeneity and far field conditions are not given.'''<br /> <br /> '''The incoming turbulence intensity is less than 0.5% for 60 ms&lt;sup&gt;-1&lt;/sup&gt;. No details on the incoming turbulence are available.'''<br /> <br /> The size of the nozzle at the entrance of the test section is 3x3 m&lt;sup&gt;2&lt;/sup&gt;.<br /> <br /> The model is supposed to be smooth. No info is available on the turbulent/laminar nature of the boundary layers on the model. The influence of possible transition can be tested by CFD;<br /> <br /> No information is available on the precision of the alignment of the model in the flow, although the symmetry on the visualizations give some confidence on this point. This sensitivity can also be checked by CFD.<br /> <br /> <br /> <br /> No details on the typical time scales are provided. The influence of the unsteadiness of the wake on the averaging process can be estimated through URANS or LES.<br /> <br /> ==='''Measurement Errors'''===<br /> <br /> Flow angle precision ± 0.4°.<br /> <br /> Free stream dynamic pressure 1%.<br /> <br /> Forces and moments are measured with balances with uncertainty of<br /> <br /> ± 0.2 N and ± 0.1Nm.<br /> <br /> <br /> ==='''Measured Data'''===<br /> <br /> The test data include measurements of:<br /> <br /> - Wall pressure<br /> <br /> - Visualization of flow patterns on rear (slant) surface<br /> <br /> - Wake survey (velocity vector plots, average values) :<br /> <br /> - Mean velocity distribution in wake central plane<br /> <br /> - Cross flow velocity for several downstream locations<br /> <br /> - Drag coefficient: contributions of the pressure and friction drags to the total drag are estimated, as well as the repartition of the pressure drag among the front, slant part and vertical base.<br /> <br /> <br /> <br /> All these data are provided for slant angles j = 5&amp;deg;, 12.5&amp;deg;, 25&amp;deg; and 30&amp;deg;.<br /> <br /> An additional test is performed by fixing a splitter plate vertically in the wake of the body, in the plane of symmetry.<br /> <br /> =='''References'''==<br /> <br /> Some salient features of the time-averaged ground vehicle wake, S.R. Ahmed, G. Ramm and G. Faltin, SAE paper series Technical paper 840300, Detroit, 1984<br /> <br /> <br /> =='''Test Case EXP-2'''==<br /> <br /> ==='''Description of Experiment'''===<br /> <br /> See table<br /> <br /> ==='''Boundary Data'''===<br /> <br /> '''The test section is a ¾ open test section. Only the floor is a solid boundary. The homogeneity and far field conditions are not given. However the blockage is assumed to be less than 4%.'''<br /> <br /> '''The incoming turbulence intensity is less than 0.25% for 40 ms&lt;sup&gt;-1&lt;/sup&gt; measured by hot wire anemometry 400 mm upstream of the model. The viscosity ratio is about 10.'''<br /> <br /> The models are supposed to be smooth. Transition to turbulence of the boundary layer on the front part is triggered.<br /> <br /> No information is available on the accuracy of the alignment of the model in the flow, although the symmetry on the visualizations give some confidence on this point. This sensitivity can also be checked by CFD.<br /> <br /> No detail on the typical time scales are provided. The influence of the unsteadiness of the wake on the averaging process can be estimated through URANS or LES.<br /> <br /> ==='''Measurement Errors'''===<br /> <br /> Error on mean velocities is less than 0.005% of local mean in the outer flow. In the wake region the accuracy is assumed to be 1% for mean values and 1.5% for RMS.<br /> <br /> <br /> ==='''Measured Data'''===<br /> <br /> LDA measurements of mean velocities: U, V, W, Reynolds stresses &lt;math&gt;\overline{u'u'}, \overline{v'v'}, \overline{w'w'}, \overline{u'v'}, \overline{u'w'}&lt;/math&gt; and third order moments &lt;math&gt;\overline{u'u'u'}, \overline{v'v'v'}, \overline{w'w'w'}, \overline{u'u'v'}, \overline{u'u'w'}, \overline{u'v'v'}, \overline{u'w'w'}&lt;/math&gt; in some planes for 2 slant angles:<br /> <br /> 25° slant angle:<br /> <br /> planes: &lt;span class=&quot;plainlinks&quot;&gt;[{{filepath:Ahmed_25_y=0_global.dat}} Ahmed_25_y=0_global.dat]&lt;/span&gt; (whole flow);<br /> &lt;span class=&quot;plainlinks&quot;&gt;[{{filepath:Ahmed_25_y=0_focus.dat}} Ahmed_25_y=0_focus.dat]&lt;/span&gt; (focus on the slant part);<br /> &lt;span class=&quot;plainlinks&quot;&gt;[{{filepath:Ahmed_25_y=100.dat}} y=100]&lt;/span&gt;; <br /> &lt;span class=&quot;plainlinks&quot;&gt;[{{filepath:Ahmed_25_y=180.dat}} y=180]&lt;/span&gt;;<br /> &lt;span class=&quot;plainlinks&quot;&gt;[{{filepath:Ahmed_25_y=195.dat}} y=195]&lt;/span&gt;;<br /> &lt;span class=&quot;plainlinks&quot;&gt;[{{filepath:Ahmed_25_y=-195.dat}} y=-195.dat]&lt;/span&gt;<br /> &lt;span class=&quot;plainlinks&quot;&gt;[{{filepath:Ahmed_25_x=-178.dat}} x=-178]&lt;/span&gt;;<br /> &lt;span class=&quot;plainlinks&quot;&gt;[{{filepath:Ahmed_25_x=-138.dat}} x=-138]&lt;/span&gt;;<br /> <br /> &lt;span class=&quot;plainlinks&quot;&gt;[{{filepath:Ahmed_25_x=-88.dat}} x=-88]&lt;/span&gt;;<br /> &lt;span class=&quot;plainlinks&quot;&gt;[{{filepath:Ahmed_25_x=-38.dat}} x=-38]&lt;/span&gt;;<br /> &lt;span class=&quot;plainlinks&quot;&gt;[{{filepath:Ahmed_25_x=0.dat}} x=0]&lt;/span&gt;;<br /> &lt;span class=&quot;plainlinks&quot;&gt;[{{filepath:Ahmed_25_x=80.dat}} x=80]&lt;/span&gt;;<br /> &lt;span class=&quot;plainlinks&quot;&gt;[{{filepath:Ahmed_25_x=200.dat}} x=200]&lt;/span&gt;;<br /> &lt;span class=&quot;plainlinks&quot;&gt;[{{filepath:Ahmed_25_x=500.dat}} x=500]&lt;/span&gt;<br /> <br /> <br /> 35° slant angle:<br /> <br /> planes: &lt;span class=&quot;plainlinks&quot;&gt;[{{filepath:Ahmed_35_y=0_global.dat}} Ahmed_35_y=0_global.dat]&lt;/span&gt; (whole flow);<br /> &lt;span class=&quot;plainlinks&quot;&gt;[{{filepath:Ahmed_35_y=0_focus.dat}} Ahmed_35_y=0_focus.dat]&lt;/span&gt; (focus on the slant part);<br /> &lt;span class=&quot;plainlinks&quot;&gt;[{{filepath:Ahmed_35_y=100.dat}} y=100]&lt;/span&gt;;<br /> &lt;span class=&quot;plainlinks&quot;&gt;[{{filepath:Ahmed_35_y=180.dat}} y=180]&lt;/span&gt;<br /> <br /> &lt;span class=&quot;plainlinks&quot;&gt;[{{filepath:Ahmed_35_x=-88.dat}} x=-88]&lt;/span&gt;;<br /> &lt;span class=&quot;plainlinks&quot;&gt;[{{filepath:Ahmed_35_x=0.dat}} x=0]&lt;/span&gt;;<br /> &lt;span class=&quot;plainlinks&quot;&gt;[{{filepath:Ahmed_35_x=80.dat}} x=80]&lt;/span&gt;;<br /> &lt;span class=&quot;plainlinks&quot;&gt;[{{filepath:Ahmed_35_x=200.dat}} x=200]&lt;/span&gt;;<br /> &lt;span class=&quot;plainlinks&quot;&gt;[{{filepath:Ahmed_35_x=500.dat}} x=500]&lt;/span&gt;<br /> <br /> <br /> <br /> Hot wire measurements in the boundary layer in the symmetry plane at different x-location: mean velocities, Reynolds stresses and third moments (only u-w components):<br /> <br /> 25° slant angle:x=<br /> &lt;span class=&quot;plainlinks&quot;&gt;[{{filepath:Ahmed_25_BL_x=-243.dat}} -243]&lt;/span&gt;,<br /> &lt;span class=&quot;plainlinks&quot;&gt;[{{filepath:Ahmed_25_BL_x=-223.dat}} -223]&lt;/span&gt;,<br /> &lt;span class=&quot;plainlinks&quot;&gt;[{{filepath:Ahmed_25_BL_x=-203.dat}} -203]&lt;/span&gt;,<br /> &lt;span class=&quot;plainlinks&quot;&gt;[{{filepath:Ahmed_25_BL_x=-183.dat}} -183]&lt;/span&gt;, <br /> &lt;span class=&quot;plainlinks&quot;&gt;[{{filepath:Ahmed_25_BL_x=-163.dat}} -163]&lt;/span&gt;,<br /> &lt;span class=&quot;plainlinks&quot;&gt;[{{filepath:Ahmed_25_BL_x=-143.dat}} -143]&lt;/span&gt;,<br /> &lt;span class=&quot;plainlinks&quot;&gt;[{{filepath:Ahmed_25_BL_x=-123.dat}} -123]&lt;/span&gt;,<br /> &lt;span class=&quot;plainlinks&quot;&gt;[{{filepath:Ahmed_25_BL_x=-103.dat}} -103]&lt;/span&gt;,<br /> &lt;span class=&quot;plainlinks&quot;&gt;[{{filepath:Ahmed_25_BL_x=-83.dat}} -83]&lt;/span&gt;,<br /> &lt;span class=&quot;plainlinks&quot;&gt;[{{filepath:Ahmed_25_BL_x=-63.dat}} -63]&lt;/span&gt;,<br /> &lt;span class=&quot;plainlinks&quot;&gt;[{{filepath:Ahmed_25_BL_x=-43.dat}} -43]&lt;/span&gt;,<br /> &lt;span class=&quot;plainlinks&quot;&gt;[{{filepath:Ahmed_25_BL_x=-23.dat}} -23]&lt;/span&gt;,<br /> &lt;span class=&quot;plainlinks&quot;&gt;[{{filepath:Ahmed_25_BL_x=-3.dat}} -3]&lt;/span&gt;<br /> <br /> 35° slant angle:x=<br /> &lt;span class=&quot;plainlinks&quot;&gt;[{{filepath:Ahmed_35_BL_x=-243.dat}} -243]&lt;/span&gt;,<br /> &lt;span class=&quot;plainlinks&quot;&gt;[{{filepath:Ahmed_35_BL_x=-223.dat}} -223]&lt;/span&gt;,<br /> &lt;span class=&quot;plainlinks&quot;&gt;[{{filepath:Ahmed_35_BL_x=-203.dat}} -203]&lt;/span&gt;,<br /> &lt;span class=&quot;plainlinks&quot;&gt;[{{filepath:Ahmed_35_BL_x=-183.dat}} -183]&lt;/span&gt;,<br /> &lt;span class=&quot;plainlinks&quot;&gt;[{{filepath:Ahmed_35_BL_x=-163.dat}} -163]&lt;/span&gt;,<br /> &lt;span class=&quot;plainlinks&quot;&gt;[{{filepath:Ahmed_35_BL_x=-143.dat}} -143]&lt;/span&gt;,<br /> &lt;span class=&quot;plainlinks&quot;&gt;[{{filepath:Ahmed_35_BL_x=-123.dat}} -123]&lt;/span&gt;,<br /> &lt;span class=&quot;plainlinks&quot;&gt;[{{filepath:Ahmed_35_BL_x=-103.dat}} -103]&lt;/span&gt;,<br /> &lt;span class=&quot;plainlinks&quot;&gt;[{{filepath:Ahmed_35_BL_x=-83.dat}} -83]&lt;/span&gt;,<br /> &lt;span class=&quot;plainlinks&quot;&gt;[{{filepath:Ahmed_35_BL_x=-63.dat}} -63]&lt;/span&gt;,<br /> &lt;span class=&quot;plainlinks&quot;&gt;[{{filepath:Ahmed_35_BL_x=-43.dat}} -43]&lt;/span&gt;,<br /> &lt;span class=&quot;plainlinks&quot;&gt;[{{filepath:Ahmed_35_BL_x=-23.dat}} -23]&lt;/span&gt;,<br /> &lt;span class=&quot;plainlinks&quot;&gt;[{{filepath:Ahmed_35_BL_x=-3.dat}} -3]&lt;/span&gt;<br /> <br /> <br /> <br /> Pressure coefficients on the rear of the body:<br /> <br /> &lt;span class=&quot;plainlinks&quot;&gt;[{{filepath:Ahmed_25_Cp.dat}} 25° slant angle]&lt;/span&gt;<br /> <br /> &lt;span class=&quot;plainlinks&quot;&gt;[{{filepath:Ahmed_35_Cp.dat}} 35° slant angle]&lt;/span&gt;<br /> <br /> <br /> <br /> &lt;span class=&quot;plainlinks&quot;&gt;[{{filepath:Inlet.dat}} Inlet.dat]&lt;/span&gt;<br /> <br /> =='''References'''==<br /> <br /> Flow and Turbulence Structures in the Wake of a Simplified Car Model (Ahmed model),<br /> <br /> H. Lienhart, C. Stoots and S. Becker, DGLR Fach Symp. Der AG STAB, Stuttgart University, 15-17 nov. 2000<br /> <br /> H. Lienhart and S. Becker, Flow and turbulence structures in the wake of a simplified car model, SAE Paper 2003-01-0656, 2003.<br /> <br /> <br /> © copyright ERCOFTAC 2004<br /> <br /> ----<br /> <br /> <br /> ''Contributors: Remi Manceau; Jean-Paul Bonnet - Université de Poitiers. &amp;mdash; Update (2024) F.R.Menter, ANSYS Germany '', <br /> <br /> Site Design and Implementation: [[Atkins]] and [[UniS]]<br /> <br /> {{AC|front=AC 1-05|description=Description_AC1-05|testdata=Test Data_AC1-05|cfdsimulations=CFD Simulations_AC1-05|evaluation=Evaluation_AC1-05|qualityreview=Quality Review_AC1-05|bestpractice=Best Practice Advice_AC1-05|relatedUFRs=Related UFRs_AC1-05}}</div> Mike https://kbwiki.ercoftac.org/w/index.php?title=Description_AC1-05&diff=45211 Description AC1-05 2024-02-14T09:46:26Z <p>Mike: </p> <hr /> <div>{{AC|front=AC 1-05|description=Description_AC1-05|testdata=Test Data_AC1-05|cfdsimulations=CFD Simulations_AC1-05|evaluation=Evaluation_AC1-05|qualityreview=Quality Review_AC1-05|bestpractice=Best Practice Advice_AC1-05|relatedUFRs=Related UFRs_AC1-05}}<br /> <br /> ='''Ahmed body'''=<br /> <br /> '''Application Challenge 1-05''' © copyright ERCOFTAC 2004<br /> <br /> <br /> <br /> =='''Introduction'''==<br /> <br /> A basic ground vehicle type of bluff body is investigated. The body consists of three parts : a fore-body, a mid section and a rear end.<br /> <br /> Two experiments are available:<br /> <br /> The first one (Exp1) was performed at DLR-Göttingen in a wind tunnel at Reynolds number 4.29 million (60 m/s), based on the model length. The model is mounted on a ground plate, in order to reproduce the ground effect. The angle of the rear end slope is adjustable, between 0 and 40° with a 5° step. More details are available for angles of 5°, 12.5° and 30°. Pressure is measured by about 210 pressure probes on the fore-body, 83 in the mid section and 450 on rear ends. Friction lines <br /> visualizations are also available. Moreover, detailed wake surveys are performed with 10 hole probes and drag measurements are provided.<br /> <br /> <br /> <br /> The second, more recent experiment (Exp2) was provided by Erlangen LSTM within the MOVA “Models for Vehicle Aerodynamics” European project (TU Delft, Univ. of Manchester (UMIST), LSTM, Electricité de France, AVL List, PSA Peugeot-Citroën). The same model is used as in the previous study, but the Reynolds number is reduced to 2.78 million (40m/s), and the study is focused on slant angles close to the drag crisis, 25° and 35°. Two-component hot wire measurements were performed in the boundary layer above the slant part and LDA measurements in 13 different planes. Mean values and turbulence statistics (second and third moments) are provided. Pressure measurements were performed on the rear part of the model (435 pressure probes). Oil/soot friction lines visualizations are also provided.<br /> <br /> The Ahmed body was one of the test cases of the 9th and 10th ERCOFTAC-IAHR Workshop on Refined Turbulence Modeling held in Darmstad, Germany (2001) and Poitiers, France (2002) respectively. These workshops were organized under the auspices of the Special Interest Group 15 on Turbulence Modeling of ERCOFTAC. The proceedings of the 10th ERCOFTAC-IAHR Workshop can be found at:<br /> <br /> [http://www.ercoftac.nl/workshop10/index.html http://www.ercoftac.nl/workshop10/index.html]<br /> <br /> and this test case at:<br /> <br /> [http://www.ercoftac.nl/workshop10/case9.4/case9.4.html http://www.ercoftac.nl/workshop10/case9.4/case9.4.html]<br /> <br /> CFD results were obtained by 15 different teams, ranging from simple RANS models (standard k-epsilon model with wall functions) to more elaborate RANS models and even LES.<br /> <br /> After the ERCOFTAC workshops in the early 2000’s, CFD simulations were mainly carried out with LES and hybrid RANS-LES methods. An update on these simulations was added in 2024 to this document by F.R. Menter including LES results for the 25° slant angle case from Menter et al (2024) - Reference see Abstract.<br /> <br /> =='''Relevance to Industrial Sector'''==<br /> <br /> The basic shape of the so-called « Ahmed body » contains important features of real road vehicles : a main body, followed by a fully separated region. Prediction of separated flows is one of the more difficult task of CFD. The parametric variation of the angle of the rear part allows the study of various configuration relevant to real car characteristics, from massively separated, “simple” wakes, to very complex, 3D wake structures. The reproduction of this complex, 3D wake is very challenging for CFD, as well as the transition from one behaviour to another. The data base contains also drag results that are essential to predict for practical purposes, and are closely related to the structure of the wake.<br /> <br /> The second set of experiments provides very detailed results, including turbulent quantities that are useful for a detailed analysis of turbulence models.<br /> <br /> <br /> =='''Design or Assessment Parameters'''==<br /> <br /> The first [[DOAP]] is the drag coefficient, and in particular its variations with the slant angle.<br /> <br /> A second [[DOAP]] is the topology of the flow, which is crucial for the correct reproduction of the drag coefficient. Comparisons between computations and experiments in the provided planes and in the boundary layer will be useful, as well as friction lines visualizations on the slant part and the vertical base.<br /> <br /> <br /> =='''Flow Domain Geometry'''==<br /> <br /> <br /> {|align=&quot;center&quot;<br /> |[[Image:Image22.gif]]<br /> |-<br /> |''Figure 1:'' Geometry of the Ahmed body <br /> |}<br /> <br /> <br /> <br /> The model is described on Figure 1. The geometry of the fore-body is available in<br /> &lt;span class=&quot;plainlinks&quot;&gt;[{{filepath:Ahmed_Front_Geo.dat}} Ahmed_Front_Geo.dat]&lt;/span&gt;.<br /> <br /> X, Y and Z are the streamwise, spanwise and ground-normal directions, respectively. The origin of the axes is the point at the intersection between the vertical base (X=0), the symmetry plane (Y=0) and the ground plate (Z=0).<br /> <br /> Overall length: 1.044 m. Width 0.389 m, Height 0.288 m.<br /> <br /> The forebody is 0.182 m long, the center of the curvature being placed 100 mm from the front and upper/lower/lateral surfaces. The central (constant section area) is 0.640 m long.<br /> <br /> All rear ends have the same slant part length Ls= 222mm. The edges are sharp.<br /> <br /> The model is placed in a 3/4-open test section (only the floor is present). No indication on the homogeneity of the flow is given.<br /> <br /> Special attention should be given on the presence of a ground plate between the tunnel floor and the body. This plate is used for preventing wind tunnel boundary layer parasitic effects on the model. The model lies 50 mm above it and is placed on stilts of 30 mm diameter.<br /> <br /> =='''Flow Physics and Fluid Dynamics Data'''==<br /> <br /> The flow has no special characteristics. Air at ambiant conditions is used. The model is supposed to be smooth.<br /> <br /> © copyright ERCOFTAC 2004<br /> <br /> ----<br /> <br /> <br /> ''Contributors: Remi Manceau; Jean-Paul Bonnet - Université de Poitiers. &amp;mdash; Update (2024) F.R.Menter, ANSYS Germany '', <br /> <br /> <br /> {{AC|front=AC 1-05|description=Description_AC1-05|testdata=Test Data_AC1-05|cfdsimulations=CFD Simulations_AC1-05|evaluation=Evaluation_AC1-05|qualityreview=Quality Review_AC1-05|bestpractice=Best Practice Advice_AC1-05|relatedUFRs=Related UFRs_AC1-05}}</div> Mike https://kbwiki.ercoftac.org/w/index.php?title=Abstr:Ahmed_body&diff=45210 Abstr:Ahmed body 2024-02-14T09:46:11Z <p>Mike: </p> <hr /> <div>{{AC|front=AC 1-05|description=Description_AC1-05|testdata=Test Data_AC1-05|cfdsimulations=CFD Simulations_AC1-05|evaluation=Evaluation_AC1-05|qualityreview=Quality Review_AC1-05|bestpractice=Best Practice Advice_AC1-05|relatedUFRs=Related UFRs_AC1-05}}<br /> <br /> == Application Area 1: External Aerodynamics ==<br /> <br /> === Application Challenge AC1-05 ===<br /> <br /> <br /> <br /> ==== Abstract ====<br /> A basic ground vehicle type of bluff body is investigated. The body consists of three parts: a fore body, a mid section and a rear end.<br /> <br /> Two experiments are available:<br /> <br /> A first one (Exp1) is performed at DLR-Göttingen in a wind tunnel at a significant Reynolds number (4.9 million for 60 m/s). The model is mounted near the wall of the wind tunnel, such that a ground effect is present. However, a ground plate is placed between the model and the floor of the wind tunnel in order to minimize this effect. The angle of the rear end slope is adjustable, between 0 and 40&amp;deg; with a 5&amp;deg; step. More details are available for angles of 5, 12.5 and 30&amp;deg;. About 210 pressure locations are available on the fore body, 83 in the mid section and 450 on rear ends. Wall flow visualizations are available. Detailed wake surveys are performed with 10 holes probes. Drag measurements are provided.<br /> <br /> A second, more recent experiment (Exp2) is provided by the Erlangen LSTM lab within the MOVA “Models for Vehicle Aerodynamics” European project (TU Delft, Univ. Of Manchester UMIST, LSTM, Electricité de France, AVL List, PSA Peugeot-Citroën). It concerns the same model as in the Ahmed study, running at 40m/s. Two-component LDV is used. Hot wire measurements are performed at 0.38 model length upstream of the model and in the boundary layer. Mean values and turbulence measurements (second and third order moments) are provided for 25&amp;deg; and 35&amp;deg; slant angle. 7,500 discrete positions are provided lying on 13 unique planes. Pressure measurements are performed on the rear part of the model.<br /> <br /> The basic shape of the so-called &amp;ldquo;Ahmed body&amp;rdquo; contains all the important features of real road vehicles: a main body, followed by a fully separated region. Prediction of separated flows is one of the more difficult task of CFD. The parametric variation of the angle of the rear part permits the simulation of various configurations relevant to real car characteristics. The complex 3D wake structure is also a challenging problem for CFD. This data base also contains drag results that are essential to prediction for practical purposes. The influence of turbulence models as well as the influence of the mesh and numerical scheme can then be tested at several levels: wall pressure, wake structure and force drag.<br /> <br /> The second set of experiments provides complementary results concerning the turbulent quantities that will be useful for a detailed analysis of turbulence models.<br /> <br /> The Design and Assessment parameters (DOAP's) for judging a CFD simulation are for this case as follows:<br /> <br /> *The first DOAP is clearly the drag coefficient computed for several slant angles.<br /> <br /> *A second DOAP is the topology of the flow, particularly the wall streamlines. Comparisons between computations and flow pattern from visualizations on the slant part will be useful. The structure of the flow will also be analyzed from the 3D representations in order to visualize the vortices.<br /> <br /> *A third DOAP will be the static pressure distributions.<br /> <br /> *A fourth DOAP will be the mean velocity distributions at several locations around and downstream of the body.<br /> <br /> *Lastly, the turbulent quantities can be considered as a DOAP; this however is more a guide for modelling than for a direct validation of codes.<br /> <br /> The Ahmed body configuration was a test case for 2 ERCOFTAC-IAHR workshops ( 2001 in Darmstadt and 2002 in Poitiers) and CFD results from 15 teams obtained for these workshops with various simple and more advanced RANS models and one LES are reported in the original test-case version produced in 2004. An update was provided in 2024 by F.R. Menter by adding LES results with accompanying documentation for the 25° slant- angle case based on the Menter et al (2024) paper.<br /> <br /> ==Reference==<br /> Menter, F.R., Hüppe, A., Flad D., Garbaruk A.V., Matyushenko A:A:, Stabnikov A:S: Large eddy simulations for the Ahmed car at 25° slant angle at different Reynolds numbers. Flow, Turbulence and Combustion, 112, 321-343, (2024).<br /> <br /> <br /> &lt;br&gt;<br /> &lt;br&gt;<br /> ----<br /> ''Contributors: Remi Manceau; Jean-Paul Bonnet - Université de Poitiers. &amp;mdash; Update (2024) F.R.Menter, ANSYS Germany '', <br /> <br /> {{AC|front=AC 1-05|description=Description_AC1-05|testdata=Test Data_AC1-05|cfdsimulations=CFD Simulations_AC1-05|evaluation=Evaluation_AC1-05|qualityreview=Quality Review_AC1-05|bestpractice=Best Practice Advice_AC1-05|relatedUFRs=Related UFRs_AC1-05}}</div> Mike https://kbwiki.ercoftac.org/w/index.php?title=AC_Index&diff=45209 AC Index 2024-02-09T11:17:18Z <p>Mike: </p> <hr /> <div>{| border=&quot;1&quot; <br /> !Application Area !!AC number!! Application Challenges !! Contributor !! Organisation <br /> |- style=&quot;background-color:#AED7FF;&quot; <br /> ![[External_Aerodynamics|External Aerodynamics]] !! !! !! !!<br /> |- style=&quot;background-color:#AED7FF;&quot; <br /> ! !! style=&quot;background-color:LightGrey;&quot;|1-01<br /> |style=&quot;background-color:LightGrey;&quot;|[[Aero-acoustic cavity]] || style=&quot;background-color:LightGrey;&quot;| Fred Mendonca || style=&quot;background-color:LightGrey;&quot;| Computational Dynamics Ltd<br /> |- style=&quot;background-color:#AED7FF;&quot; <br /> ! !! style=&quot;background-color:LightGrey;&quot;|1-02<br /> | style=&quot;background-color:LightGrey;&quot;|[[RAE M2155 Wing]] || style=&quot;background-color:LightGrey;&quot;| Pietro Catalano, Anthony Hutton || style=&quot;background-color:LightGrey;&quot;| CIRA, Qinetiq<br /> |- style=&quot;background-color:#AED7FF;&quot; <br /> ! !! style=&quot;background-color:LightGrey;&quot;|1-05<br /> | style=&quot;background-color:LightGrey;&quot;|[[Ahmed body]] || style=&quot;background-color:LightGrey;&quot;| Jean-Paul Bonnet, Remi Manceau, F.R.Menter || style=&quot;background-color:LightGrey;&quot;| Université de Poitiers, ANSYS Germany<br /> |- style=&quot;background-color:#AED7FF;&quot; <br /> ! !! style=&quot;background-color:LightGrey;&quot;|1-08<br /> | style=&quot;background-color:LightGrey;&quot;|[[L1T2 3 element airfoil]]&lt;!--[[Image:Star_red.jpg]]--&gt; || style=&quot;background-color:LightGrey;&quot;| Jan Vos, Anthony Hutton || style=&quot;background-color:LightGrey;&quot;| CFS Engineering SA, Qinetiq<br /> |- style=&quot;background-color:#AED7FF;&quot; <br /> ! !! style=&quot;background-color:LightGrey;&quot;|1-09<br /> | style=&quot;background-color:LightGrey;&quot;|[[AC1-09|Vortex breakdown above a delta wing with sharp leading edge]] &lt;!--[[Image:Star_red.jpg]]--&gt;|| style=&quot;background-color:LightGrey;&quot;| Johan Kok ''et al.'' || style=&quot;background-color:LightGrey;&quot;| NLR<br /> |- style=&quot;background-color:#AED7FF;&quot; <br /> ![[Combustion|Combustion]] !! !! !! !!<br /> |- style=&quot;background-color:#AED7FF;&quot; <br /> ! !! style=&quot;background-color:LightGrey;&quot;|2-01<br /> | style=&quot;background-color:LightGrey;&quot;|[[Bluff body burner for CH4-HE turbulent combustion]] || style=&quot;background-color:LightGrey;&quot;| Elisabetta Belardini || style=&quot;background-color:LightGrey;&quot;| Universita di Firenze <br /> |- style=&quot;background-color:#AED7FF;&quot; <br /> ! !! style=&quot;background-color:LightGrey;&quot;|2-06<br /> | style=&quot;background-color:LightGrey;&quot;|[[The confined TECFLAM swirling natural gas burner]] || style=&quot;background-color:LightGrey;&quot;| Stefan Hohmann || style=&quot;background-color:LightGrey;&quot;| MTU Aero Engines<br /> <br /> |- style=&quot;background-color:#AED7FF;&quot; <br /> ! !! style=&quot;background-color:LightGrey;&quot;|2-07<br /> | style=&quot;background-color:LightGrey;&quot;|[[Confined double annular jet]] || style=&quot;background-color:LightGrey;&quot;| Charles Hirsch || style=&quot;background-color:LightGrey;&quot;| Vrije Universiteit Brussel<br /> <br /> |- style=&quot;background-color:#AED7FF;&quot;<br /> ! !! style=&quot;background-color:LightGrey;&quot;|2-08<br /> | style=&quot;background:LightGrey;&quot;|[[Premixed Methane-Air Swirl Burner (TECFLAM)]]&lt;!--[[Image:Star_red.jpg]]--&gt;||style=&quot;background-color:LightGrey;&quot; | Guido&amp;nbsp;Kuenne, Andreas&amp;nbsp;Dreizler, Johannes&amp;nbsp;Janicka || style=&quot;background-color:LightGrey;&quot;| Darmstadt University of Technology<br /> <br /> |- style=&quot;background-color:#AED7FF;&quot;<br /> ! !! style=&quot;background-color:LightGrey;&quot;|2-09<br /> | style=&quot;background:LightGrey;&quot;|[[SANDIA Flame D]]&lt;!--[[Image:Star_red.jpg]]--&gt;||style=&quot;background-color:LightGrey;&quot;| Andrzej Boguslawski, Artur Tyliszczak|| style=&quot;background-color:LightGrey;&quot;|Częstochowa University of Technology<br /> <br /> |- style=&quot;background-color:#AED7FF;&quot;<br /> ! !! style=&quot;background-color:LightGrey;&quot;|2-10<br /> | style=&quot;background:LightGrey;&quot;|[[Internal combustion engine flows for motored operation]] ||style=&quot;background-color:LightGrey;&quot;| Carl Philip Ding ''et al.'' ||style=&quot;background-color:LightGrey;&quot;| Technische Universit&amp;auml;t Darmstadt<br /> <br /> |- style=&quot;background-color:#AED7FF;&quot;<br /> ! !! style=&quot;background-color:LightGrey;&quot;|2-11<br /> | style=&quot;background:LightGrey;&quot;| [[AC2-11|Delft-Jet-in-Hot-Coflow (DJHC) burner]] ||style=&quot;background-color:LightGrey;&quot;|Andr&amp;eacute; Perpignan ''et al.''||style=&quot;background-color:LightGrey;&quot;| TU Delft<br /> <br /> |- style=&quot;background-color:#AED7FF;&quot;<br /> ! !! style=&quot;background-color:LightGrey;&quot;|2-12<br /> | style=&quot;background:LightGrey;&quot;|[[AC2-12|AC2-12 Turbulent separated inert and reactive flows over a triangular bluff body]] ||style=&quot;background-color:LightGrey;&quot;| D.A. Lysenko and M. Donskov ||style=&quot;background-color:LightGrey;&quot;|3DMSimtek AS, Sandnes, Norway<br /> <br /> |- style=&quot;background-color:#AED7FF;&quot; <br /> ![[Chemical%2C_Process%2C_Thermal_and_Nuclear_Safety|Chemical &amp; Process, Thermal Hydraulics &amp; Nuclear Safety]] !! !! !! !!<br /> |- style=&quot;background-color:#AED7FF;&quot; <br /> ! !! style=&quot;background-color:LightGrey;&quot;|3-01<br /> | style=&quot;background-color:LightGrey;&quot;|[[Buoyancy-opposed wall jet]] || style=&quot;background-color:LightGrey;&quot;| Jeremy Noyce || style=&quot;background-color:LightGrey;&quot;| Magnox Electric<br /> |- style=&quot;background-color:#AED7FF;&quot; <br /> ! !! style=&quot;background-color:LightGrey;&quot;|3-02<br /> | style=&quot;background-color:LightGrey;&quot;|[[Induced flow in a T-junction]] || style=&quot;background-color:LightGrey;&quot;| Frederic Archambeau || style=&quot;background-color:LightGrey;&quot;| EDF - R&amp;D Division<br /> |- style=&quot;background-color:#AED7FF;&quot; <br /> ! !! style=&quot;background-color:LightGrey;&quot;|3-03<br /> | style=&quot;background-color:LightGrey;&quot;|[[Cyclone separator]] || style=&quot;background-color:LightGrey;&quot;| Chris Carey || style=&quot;background-color:LightGrey;&quot;| Fluent Europe Ltd<br /> |- style=&quot;background-color:#AED7FF;&quot; <br /> ! !! style=&quot;background-color:LightGrey;&quot;|3-08<br /> | style=&quot;background-color:LightGrey;&quot;|[[Spray evaporation in turbulent flow]]&lt;!--[[Image:star_red.jpg]]--&gt;|| style=&quot;background-color:LightGrey;&quot;| Martin Sommerfeld || style=&quot;background-color:LightGrey;&quot;| Martin-Luther-Universitat Halle-Wittenberg<br /> |- style=&quot;background-color:#AED7FF;&quot; <br /> ! !! style=&quot;background-color:LightGrey;&quot;|3-10<br /> | style=&quot;background-color:LightGrey;&quot;|[[Combining/dividing flow in Y junction]] || style=&quot;background-color:LightGrey;&quot;| Lewis Davenport || style=&quot;background-color:LightGrey;&quot;| Rolls-Royce Marine Power, Engineering &amp; Technology Division<br /> |- style=&quot;background-color:#AED7FF;&quot; <br /> ! !! style=&quot;background-color:LightGrey;&quot;|3-11<br /> | style=&quot;background-color:LightGrey;&quot;|[[Downward flow in a heated annulus]] || style=&quot;background-color:LightGrey;&quot;| Mike Rabbitt || style=&quot;background-color:LightGrey;&quot;| British Energy<br /> |- style=&quot;background-color:#AED7FF;&quot; <br /> ! !! style=&quot;background-color:LightGrey;&quot;|3-12<br /> | style=&quot;background-color:LightGrey;&quot;|[[AC3-12|Particle-laden swirling flow]]&lt;!--[[Image:star_red.jpg]]--&gt;|| style=&quot;background-color:LightGrey;&quot;| Martin Sommerfeld || style=&quot;background-color:LightGrey;&quot;| Martin-Luther-Universitat Halle-Wittenberg<br /> |- style=&quot;background-color:#AED7FF;&quot; <br /> ![[Civil_Construction_and_HVAC|Civil Construction &amp; HVAC]] !! !! !! !!<br /> |- style=&quot;background-color:#AED7FF;&quot; <br /> ! !! style=&quot;background-color:LightGrey;&quot;|4-01<br /> | style=&quot;background-color:LightGrey;&quot;|[[Wind environment around an airport terminal building]]&lt;!--[[Image:star_red.jpg]]--&gt;|| style=&quot;background-color:LightGrey;&quot;| Steve Gilham, Athena Scaperdas || style=&quot;background-color:LightGrey;&quot;| Atkins<br /> |- style=&quot;background-color:#AED7FF;&quot; <br /> ! !! style=&quot;background-color:LightGrey;&quot;|4-02<br /> | style=&quot;background-color:LightGrey;&quot;|[[Flow and Sediment Transport in a Laboratory Model of a stretch of the Elbe River]] || style=&quot;background-color:LightGrey;&quot;| Wolfgang Rodi || style=&quot;background-color:LightGrey;&quot;| Universität Karlsruhe<br /> |- style=&quot;background-color:#AED7FF;&quot; <br /> ! !! style=&quot;background-color:LightGrey;&quot;|4-03<br /> | style=&quot;background-color:LightGrey;&quot;|[[Air flows in an open plan air conditioned office]]&lt;!--[[Image:star_red.jpg]]--&gt;|| style=&quot;background-color:LightGrey;&quot;| Isabelle Lavedrine, Darren Woolf || style=&quot;background-color:LightGrey;&quot;| Arup<br /> |- style=&quot;background-color:#AED7FF;&quot; <br /> ! !! style=&quot;background-color:LightGrey;&quot;|4-04<br /> | style=&quot;background-color:LightGrey;&quot;|[[Tunnel fire]] || style=&quot;background-color:LightGrey;&quot;| Nicholas Waterson || style=&quot;background-color:LightGrey;&quot;| Mott MacDonald Ltd<br /> |- style=&quot;background-color:#AED7FF;&quot; <br /> ![[Environmental_Flow|Environmental Flows]] !! !! !! !!<br /> |- style=&quot;background-color:#AED7FF;&quot; <br /> ! !! style=&quot;background-color:LightGrey;&quot;|5-05<br /> | style=&quot;background-color:LightGrey;&quot;|[[Boundary layer flow and dispersion over isolated hills and valleys]] &lt;!--[[Image:star_red.jpg]]--&gt;|| style=&quot;background-color:LightGrey;&quot;| Ian Castro|| style=&quot;background-color:LightGrey;&quot;| University of Southampton <br /> |- style=&quot;background-color:#AED7FF;&quot; <br /> ![[Turbomachinery_Internal_Flow|Turbo-machinery Internal Flows]] !! !! !! !!<br /> |- style=&quot;background-color:#AED7FF;&quot; <br /> ! !! style=&quot;background-color:LightGrey;&quot;|6-02 <br /> | style=&quot;background-color:LightGrey;&quot;|[[Low-speed centrifugal compressor]] || style=&quot;background-color:LightGrey;&quot;| Nouredine Hakimi || style=&quot;background-color:LightGrey;&quot;| NUMECA International<br /> |- style=&quot;background-color:#AED7FF;&quot; <br /> ! !! style=&quot;background-color:LightGrey;&quot;|6-05<br /> | style=&quot;background-color:LightGrey;&quot;|[[Annular compressor cascade with tip clearance]] || style=&quot;background-color:LightGrey;&quot;| K. Papailiou || style=&quot;background-color:LightGrey;&quot;| NTUA<br /> |- style=&quot;background-color:#AED7FF;&quot; <br /> ! !! style=&quot;background-color:LightGrey;&quot;|6-06<br /> | style=&quot;background-color:LightGrey;&quot;|[[Gas Turbine nozzle cascade]] || style=&quot;background-color:LightGrey;&quot;| Elisabetta Belardini, Francesco Martelli || style=&quot;background-color:LightGrey;&quot;| Universita di Firenze<br /> |- style=&quot;background-color:#AED7FF;&quot; <br /> ! !! style=&quot;background-color:LightGrey;&quot;|6-07<br /> | style=&quot;background-color:LightGrey;&quot;|[[Draft tube]] || style=&quot;background-color:LightGrey;&quot;| Jan Eriksson, Rolf Karlsson || style=&quot;background-color:LightGrey;&quot;| Vattenfall Utveckling AB<br /> |- style=&quot;background-color:#AED7FF;&quot; <br /> ! !! style=&quot;background-color:LightGrey;&quot;|6-08<br /> | style=&quot;background-color:LightGrey;&quot;|[[High speed centrifugal compressor]] || style=&quot;background-color:LightGrey;&quot;|Beat Ribi, Michael Casey || style=&quot;background-color:LightGrey;&quot;| MAN Turbomaschinen AG Schweiz , Sulzer Innotec AG<br /> |- style=&quot;background-color:#AED7FF;&quot; <br /> ! !! style=&quot;background-color:LightGrey;&quot;|6-10<br /> | style=&quot;background-color:LightGrey;&quot;|[[Axial compressor cascade]] || style=&quot;background-color:LightGrey;&quot;| Fred Mendonca || style=&quot;background-color:LightGrey;&quot;| Computational Dynamics Ltd<br /> |- style=&quot;background-color:#AED7FF;&quot; <br /> ! !! style=&quot;background-color:LightGrey;&quot;|6-12<br /> | style=&quot;background-color:LightGrey;&quot;|[[Steam turbine rotor cascade]] || style=&quot;background-color:LightGrey;&quot;| Jaromir Prihoda || style=&quot;background-color:LightGrey;&quot;| Czech Academy of Sciences<br /> |- style=&quot;background-color:#AED7FF;&quot; <br /> ! !! style=&quot;background-color:LightGrey;&quot;|6-14<br /> | style=&quot;background-color:LightGrey;&quot;|[[AC6-14|Swirling flow in a conical diffuser generated with rotor-stator interaction]] &lt;!--[[Image:Star_red.jpg]]--&gt;|| style=&quot;background-color:LightGrey;&quot;| A. Javadi ''et al'' || style=&quot;background-color:LightGrey;&quot;| Chalmers University of Technology, G&amp;ouml;teborg, Sweden;<br /> |- style=&quot;background-color:#AED7FF;&quot;<br /> ! !! style=&quot;background-color:LightGrey;&quot;|6-15<br /> | style=&quot;background-color:LightGrey;&quot;|[[AC6-15|Vortex ropes in draft tube of a laboratory Kaplan hydro turbine at low load]] || style=&quot;background-color:LightGrey;&quot;|A.V. Minakov ''et al.'' || style=&quot;background-color:LightGrey;&quot;| Institute of Thermophysics SB RAS, Novosibirsk, Russia<br /> |- style=&quot;background-color:#AED7FF;&quot; <br /> ![[Biomedical_Flows|Biomedical Flows]] !! !! !! !!<br /> |- style=&quot;background-color:#AED7FF;&quot;<br /> ! !! style=&quot;background-color:LightGrey;&quot;|7-01 <br /> | style=&quot;background-color:LightGrey;&quot;|[[AC7-01|Aerosol deposition in the human upper airways]] || style=&quot;background-color:LightGrey;&quot;| P. Koullapis ''et al.'' || style=&quot;background-color:LightGrey;&quot;| University of Cyprus<br /> |- style=&quot;background-color:#AED7FF;&quot; <br /> ! !! style=&quot;background-color:LightGrey;&quot;|7-02 <br /> | style=&quot;background-color:LightGrey;&quot;|[[AC7-02|Airflow in the human upper airways]] || style=&quot;background-color:LightGrey;&quot;| P. Koullapis ''et al.'' || style=&quot;background-color:LightGrey;&quot;| University of Cyprus <br /> |- style=&quot;background-color:#AED7FF;&quot; <br /> ! !! style=&quot;background-color:LightGrey;&quot;|7-03 <br /> | style=&quot;background-color:LightGrey;&quot;|[[AC7-03|Flow in a Ventricular Assist Device - Pump Performance &amp; Blood Damage Prediction]] || style=&quot;background-color:LightGrey;&quot;| B. Torner || style=&quot;background-color:LightGrey;&quot;| University of Rostock, Germany<br /> |- style=&quot;background-color:#AED7FF;&quot; <br /> ! !! style=&quot;background-color:LightGrey;&quot;|7-04 <br /> | style=&quot;background-color:LightGrey;&quot;|[[AC7-04|A pulsatile 3D flow relevant to thoracic hemodynamics: CFD - 4D Flow MRI comparison]] || style=&quot;background-color:LightGrey;&quot;| Morgane Garreau || style=&quot;background-color:LightGrey;&quot;| University of Montpellier, France <br /> |}</div> Mike https://kbwiki.ercoftac.org/w/index.php?title=Evaluation_AC1-05&diff=45208 Evaluation AC1-05 2024-02-09T11:16:24Z <p>Mike: </p> <hr /> <div>{{AC|front=AC 1-05|description=Description_AC1-05|testdata=Test Data_AC1-05|cfdsimulations=CFD Simulations_AC1-05|evaluation=Evaluation_AC1-05|qualityreview=Quality Review_AC1-05|bestpractice=Best Practice Advice_AC1-05|relatedUFRs=Related UFRs_AC1-05}}<br /> <br /> ='''Ahmed body'''=<br /> <br /> '''Application Challenge 1-05''' © copyright ERCOFTAC 2004<br /> <br /> <br /> <br /> =='''Comparison of Test data and CFD'''==<br /> <br /> Experiments provide very detailed data that offer a particularly difficult challenge to CFD. They showed that the drag crisis experienced by the body around 25°-30° is related to a dramatic change of the structure of the wake. The low-drag configuration (35°) consists in a massively separated wake, which is quasi-2D, while the high-drag configuration (25°) consists in a very complex, 3D wake structure, with a reattachment of the flow on the slant part and a strong interaction of the bubble with intense corner vortices, which are very energy-consuming.<br /> <br /> EXP1 shows that fixing a splitter plate in the wake of the body, in the symmetry plane, forces the flow to turn back to the low drag configuration (massively separated wake). The mechanism underlying these phenomena is not clear, but it could be due to the fact that the splitter plate counteracts a flapping of the wake in the span-wise direction. Therefore, there are some evidences that large-scale unsteadiness of the wake could play a crucial role in the wake structure transition. It could also explain high levels of turbulent stresses above the slant part that are very difficult to predict with steady-state RANS calculations.<br /> <br /> It appears from all the CFD results that the wake structure of the low drag configurations (35°) is correctly reproduced by all the turbulence models tested. The correct trend of the drag coefficient with the slant angle is correctly reproduced (CFD1), but the correct level is not found. In general, since the wake structure is correct, the pressure levels on the slant part are realistic, but the exact pressure repartition on the slant part and the vertical base are hardly reproduced.<br /> <br /> <br /> Concerning the high-drag configuration (25°), the great majority of the CFD computations were not able to reproduce the complex, 3D structure of the wake: a massively separated wake is obtained, which shows that the wake structure transition is missed. The number of computation and the variety of numerical schemes and meshes give many indications that the main issue is not numerical, but linked to the physical modeling: turbulence model and steady-state strategy. It appears that only two types of modeling are able to reproduce the structure of the wake: LES (CFD9) and low-Reynolds number Reynolds stress model (CFD13). It should indicate that the large-scale unsteadiness of the wake must be resolved (the potential of URANS has not been investigated extensively yet) or, alternatively, the absence of large-scale unsteadiness resolution must be compensated by a very refined turbulence modeling (Reynolds stress transport equations and integration down to the wall). However, these partial conclusions are only based on one LES and one low-Re RSM computation. Additional studies are necessary to confirm these favorable conclusions.<br /> <br /> <br /> The paper of Florian Menter extracted from the Proceedings of the 10th ERCOFTAC IAHR Workshop (http://www.ercoftac.nl/workshop10/index.html) with permission, gives a further comparison of experimental and CFD results, including various figures. This paper can be obtained by clicking [{{filepath:Ahmed.florian.menter.pdf}} here].<br /> <br /> ==='''Update added in 2024 by F.R. Menter'''===<br /> <br /> Since the ERCOFTAC workshops, simulations have progressed with an increased focus on Scale-Resolving Simulations. The simulations fall in two categories: Hybrid RANS-LES model and pure LES model simulations. Hybrid RANS-LES methods seem well suited for the Ahmed 25° car. They avoid the high cost of LES near the wall of the attached boundary layers. The ability of such models to predict the complex flow topology for the 25° case depends however on the ability of the underlying RANS model to predict separation from the slant onset. For a discussion of hybrid methods with application to this current test case see e.g. [https://hal.science/hal-02874819/document Guilminesau et al. (2020)], [https://www.sciencedirect.com/science/article/pii/S0167610520302117 Ekman et al. (2020)].<br /> <br /> The application of LES to the 25° case proved surprisingly difficult. Up to the publication by [https://link.springer.com/article/10.1007/s10494-023-00472-9 Menter et al (2024)] no LES with acceptable accuracy for the exp. Reynolds number has been achieved. For a review of LES studies see [https://link.springer.com/article/10.1007/s10494-023-00472-9 Menter et al (2024)]. Of special interest is that simulations at artificially reduced Reynolds number were able to predict the correct flow topology with separation and reattachment on the slant, even on coarse grids. However, at the exp. Reynolds number, the simulations showed a similar behavior to RANS models. In one set of simulations, the flow stayed attached (like with k- type models) and in another set, the flow stalled (like with SST type models). The authors in [https://link.springer.com/article/10.1007/s10494-023-00472-9 Menter et al (2024)] confirmed this observation, even for much finer meshes than used previously (e.g. a 560 million block-structured hexahedral mesh resulted in fully attached flow). Only after turning to Octree meshes, which allow a three-dimensional refinement towards the wall, could a sufficient resolution of the boundary layer be achieved to allow a reliable prediction of separation and reattachment on the slant. The following pictures are taken from [https://link.springer.com/article/10.1007/s10494-023-00472-9 Menter et al (2024)].<br /> <br /> {|align=&quot;center&quot;<br /> |[[Image:Ac1_05_figure_2.png|600px|center|]]<br /> |-<br /> |''Figure 2:'' Zoom of Octree meshes O1 and O2 near the roof-slant intersection. <br /> |}<br /> <br /> {|align=&quot;center&quot;<br /> |[[Image:Ac1_05_figure_3a.png|600px|center|]]<br /> |-<br /> |[[Image:Ac1_05_figure_3b.png|600px|center|]]<br /> |-<br /> |''Figure 3:'' Flow structure on roof-center plane for WALE O1(top) and WALE O2 (bottom) meshes showing contours of vorticity. <br /> |}<br /> <br /> {|align=&quot;center&quot;<br /> |[[Image:Ac1_05_figure_4.png|600px|center|]]<br /> |-<br /> |''Figure 4:'' Wall shear stress on the roof-center plane for WALE- O2 and WALE- O1 in comparison with SBES/RANS solution. <br /> |}<br /> <br /> <br /> Fig. 2 shows two Octree meshes near the roof-slant onset of the Ahmed car. The coarser mesh has 230 million and the refined mesh has 320 million cells. Both grids are formally of sufficient near-wall resolution for a wall-resolved LES (with ∆x^+=∆z^+≈35,∆y^+=1 in streamwise, spanwise and wall-normal direction respectively). However, the 320 million cell mesh (O1) has an overall finer mesh in the central part of the boundary layer. This results in a resolution of finer turbulence structures in the roof boundary layer as seen in Fig.3. The improved resolution brings the LES closer to the wall shear stress distribution (Cf) of the SST/SBES model which can serve as a reliable reference for the zero-pressure gradient flow in that region (Fig.4).<br /> <br /> <br /> {|align=&quot;center&quot;<br /> |[[Image:Ac1_05_figure_5.png|600px|center|]]<br /> |-<br /> |''Figure 5:'' Velocity profiles in center plane for WRLES on O1 and O2 grids, compared to experimental data. <br /> |}<br /> <br /> {|align=&quot;center&quot;<br /> |[[Image:Ac1_05_figure_6.png|600px|center|]]<br /> |-<br /> |''Figure 6:'' Stress profiles for streamwise coordinate in center plane for WRLES on O1 and O2 grids, compared to experimental data. <br /> |}<br /> <br /> Both meshes produce highly accurate representations of the separation bubble on the slant as seen from the velocity profiles in Fig. 5. Included in the figure is also a simulation on the O1 mesh where the WALE model was deactivated in the entire domain, which resulted in an even slightly better agreement with the experimental data. Fig. 6 shows the corresponding profiles for the streamwise stress component, which are again in good agreement with the experimental data, in contrast to RANS models which strongly underpredicted the stress level. While there are acceptable velocity profile results available for hybrid models e.g. [https://hal.science/hal-02874819/document Guilmineau et al. (2020)], also none of these simulations captures the correct stress-level, especially just downstream of the slant onset. This points to a high consistency of the depicted LES simulations. <br /> <br /> <br /> {|align=&quot;center&quot;<br /> |[[Image:Ac1_05_figure_7a.png|400px]][[Image:Ac1_05_figure_7b.png|400px]]<br /> |-<br /> |''Figure 7:'' : Flow topology on slant of Ahmed car. Left: experimental oil flow (from Ahmed et al 1984). Right: Octree O1 – no model simulation. <br /> |}<br /> <br /> Figure 7 shows the flow topology for the O1 (no model) simulation compared to the experimental oil flow. As expected from the close agreement in the velocity profiles, the agreement in the flow pattern is also very close. <br /> <br /> <br /> {|align=&quot;center&quot;<br /> |[[Image:Ac1_05_figure_8.png|600px|center|]]<br /> |-<br /> |''Figure 8:'' Q-criterion plots for Octree O1 no model solution. Large picture has &lt;math&gt;Q=5 \cdot 10^6s^{-2}&lt;/math&gt; and smaller picture has &lt;math&gt;Q=1 \cdot 10^8s^{-2}&lt;/math&gt;. <br /> |}<br /> <br /> Finally, Figure 8 shows the resolved turbulence structures using the Q-criterion with a zoom to the slant onset region for the O1 mesh. As seen, this mesh allows for a very fine resolution of the turbulence which is necessary to accurately capture flow reattachment. <br /> <br /> =='''References'''==<br /> Ekman , P., Wieser, D., Virdung, T., Karlsson, M., Assessment of hybrid RANS-LES methods for accurate aerodynamic simulations. J. of wind Engg. And Industrial Aerodynamics, 206, (2020), 104301.<br /> <br /> Guilmineau E., Deng G.B., Leroyer A., Queutey P. Visonneau M., Wackers J., Assessment of hybrid RANS-LES formulations for flow simulation around the Ahmed body. Comput. Fluids 176, 302-319 (2018) <br /> <br /> Menter,F.R., Hüppe A., Flad D., Garburak, A. V., Matyushenko A.A., Stabnikov A.S., Large eddy simulations for the Ahmed car at 25° slant angle at different Teynolds numbers. Flow, Turbulence and Combustion, 112, 321-343, (2024).<br /> <br /> © copyright ERCOFTAC 2004<br /> <br /> <br /> ----<br /> <br /> ''Contributors: Remi Manceau; Jean-Paul Bonnet - Université de Poitiers. Update (2024) F.R.Menter, ANSYS Germany'', <br /> <br /> <br /> {{AC|front=AC 1-05|description=Description_AC1-05|testdata=Test Data_AC1-05|cfdsimulations=CFD Simulations_AC1-05|evaluation=Evaluation_AC1-05|qualityreview=Quality Review_AC1-05|bestpractice=Best Practice Advice_AC1-05|relatedUFRs=Related UFRs_AC1-05}}</div> Mike https://kbwiki.ercoftac.org/w/index.php?title=Best_Practice_Advice_AC1-05&diff=45207 Best Practice Advice AC1-05 2024-02-09T11:12:50Z <p>Mike: </p> <hr /> <div>{{AC|front=AC 1-05|description=Description_AC1-05|testdata=Test Data_AC1-05|cfdsimulations=CFD Simulations_AC1-05|evaluation=Evaluation_AC1-05|qualityreview=Quality Review_AC1-05|bestpractice=Best Practice Advice_AC1-05|relatedUFRs=Related UFRs_AC1-05}}<br /> <br /> ='''Ahmed body'''=<br /> <br /> '''Application Challenge 1-05''' © copyright ERCOFTAC 2004<br /> <br /> <br /> <br /> =='''Best Practice Advice for the AC'''==<br /> <br /> ==='''Key Fluid Physics'''===<br /> <br /> ==='''A-Key design or assessment parameters [[DOAP]] :'''===<br /> <br /> <br /> <br /> • The Drag coefficient Cd, and in particular its variations with the slant angle (see figure), is the main global parameter to be predicted.<br /> <br /> [[Image:D34_image2.jpg]] <br /> <br /> <br /> <br /> The topology of the flow is crucial for the correct reproduction of the drag coefficient: in particular, the drag crisis around 25-30° corresponds to a transition of the wake structure from a massively separated, quasi-2D structure to a complex, 3D structure.<br /> <br /> <br /> <br /> <br /> <br /> '''B- Key physics :'''<br /> <br /> <br /> <br /> • The contributions of the different components of the drag have different trends when the slant angle changes (see figure).<br /> <br /> <br /> <br /> <br /> <br /> • The component responsible for the drag crisis is the pressure drag due to the slant part , which jumps from 35% of total drag at 35° to 55% at 25°.<br /> <br /> <br /> <br /> <br /> <br /> • The drag crisis corresponds to a dramatic change is the structure of the wake:<br /> <br /> o In the low-drag configuration, the wake is massively-separated, quasi-toroïdal<br /> <br /> o <br /> [[Image:D34_image4.jpg]]<br /> <br /> <br /> <br /> In the high-drag configuration, the wake has a complex, 3D structure: in the central region of the slant part (close to the symmetry plane) experiments show a small separation bubble, with a reattachement on the slant part. This bubble strongly interacts with the highly energetic corner vortices. Other complex phenomena are present (interaction with the underside flow, with side boundary layers, large-scale flapping in the spanwise direction, etc.), but they are not well understood yet.<br /> <br /> <br /> <br /> <br /> <br /> <br /> <br /> '''C- Comparison of CFD and experiments'''<br /> <br /> <br /> <br /> • '''Low-drag configuration (35°):'''<br /> <br /> o Realistic pressure level and distribution on the slant part and vertical base are predicted, even with standard k-epsilon with wall functions<br /> <br /> o The correct trend of the drag with the slant angle is obtained<br /> <br /> o However, quantitative predictions are not correct: pressure drop and drag are generally underestimated<br /> <br /> <br /> <br /> <br /> <br /> • '''High-drag configuration (25°):'''<br /> <br /> o The wake structure transition is missed by almost all models, whatever the numerical accuracy and the conditions of the computation: pressure drop on the base is highly underestimated. Only LES and low-Re RSM are able to reproduce the complex, 3D wake structure but:<br /> <br /> o LES (CFD9) does not reproduce correctly the boundary layer, because of the use of wall functions<br /> <br /> o Low-Re RSM (CFD13) overpredicts the reattachment length and the independance to numerics is not validated enough to draw definitive conclusions<br /> <br /> <br /> ==='''Application Uncertainties'''===<br /> <br /> • The influence of the stilts on the drag is at least 10% (CFD11), but their influence on the structure of the flow under the body is not known precisely, and this may have a significant influence on the wake of the body, which cannot be evaluated.<br /> <br /> • The experiments were performed in a ¾ open test section. The influence of using a finite computational domain is not known.<br /> <br /> ==='''Computational Domain and Boundary Conditions'''===<br /> <br /> '''Computational domain'''<br /> <br /> • ½ body (symmetry) is sufficient for steady-state computations (RANS). Use the full body for unsteady computations (LES, URANS).<br /> <br /> • CFD11 estimates that the stilts roughly contribute to 10% of the drag. Stilts must be included.<br /> <br /> • Include the ground plate: CFD3 shows that the flow without a ground plate is completely different. The ground plate should start 2L (L=body length) in front of the body to mimic the EXP2 profiles (CFD11, CFD15) (however, the importance of this condition has not been demonstrated).<br /> <br /> • Inlet must be placed before x=-3L. Outlet must be sufficiently far to have no influence on the wake: outlet at x=5L is generally used, but no systematic study have been performed.<br /> <br /> • Side and top boundaries: blockage is estimated to 4% in the experiments. To avoid too much blockage in CFD, the minimal recommended cross-section is 2Lx1.35L (for the full body).<br /> <br /> <br /> <br /> '''Boundary conditions'''<br /> <br /> • Use low turbulence intensity at the inlet and small viscosity ratio (I=0.25% and nt / n=10 estimated by EXP2).<br /> <br /> • CFD11 shows that boundary conditions allowing outflow through the side and top boundaries are preferable to slip walls.<br /> <br /> <br /> ==='''Discretisation and Grid Resolution'''===<br /> <br /> '''Discretisation method'''<br /> <br /> • Convection scheme sensitivity studies (CFD11) and comparaison between different teams using the same model and the same mesh show that for the type of grids described below (“marginal resolution”), the solution is sensitive to the convection scheme. Use 2nd order approximation.<br /> <br /> • Sensitivity to other sources of numerical errors (non-orthogonal cells, interpolations, explicit terms) are suspected: care must be taken to avoid 1st order sources of error.<br /> <br /> • Time marching: second order time marching is also advised for unsteady computations, though it is no supported by clear sensitivity studies.<br /> <br /> <br /> <br /> <br /> <br /> '''Grid resolution'''<br /> <br /> • Meshes used in the CFD studies are very complex and precise specifications cannot be given. A grid sensitivity study is strongly advised, since the predictions are very sensitive to the mesh resolution. However, from sensitivity studies and comparisons between computations from different teams with the same models, the following guidelines can be provided (this are minimal constraints to reach an acceptable level of numerical error for global quantities like Cd, not for more sensitive quantities like velocities in the boundary layer):<br /> <br /> o Surface mesh: at least 15000 cells are necessary, which leads to:<br /> <br /> o Volume mesh: at least 0.5x106 cells for high-Re models (y+&gt;30) and at least 1.5x106 cells for low-Re models (y+=1)<br /> <br /> These guidelines are for ½ the body (double the cell number for the full body).<br /> <br /> <br /> ==='''Physical Modelling'''===<br /> <br /> In the Ahmed body test case, predicting correctly the overall quantities (Cd, wake structure) is already a challenge. Therefore, giving advice for predicting flow details would be irrelevant:<br /> <br /> <br /> <br /> '''BPA for overall quantities'''<br /> <br /> • '''Low-drag configurations'''<br /> <br /> All the turbulence models used in the CFD studies give a correct wake structure and Cd trend when varying the angle for low-drag configurations. However, using low-Re models gives a better boundary layer prediction on the slant part. None of the models give the correct quantitative prediction of the pressure distribution on the slant part and vertical base, and, therefore, of the drag.<br /> <br /> o For qualitative predictions in the low-drag configuration, simple eddy-viscosity models with wall functions are sufficient<br /> <br /> o Quantitative predictions cannot be trusted, whatever the model<br /> <br /> <br /> <br /> • '''High-drag configuration'''<br /> <br /> High Reynolds number models (k-ε, RSM) with wall functions must be avoided, because they generally do not predict separation at all, and always fail predicting correct profiles above the slant part.<br /> <br /> Low-Re eddy-viscosity models predict separation provided they are free from the usual stagnation point anomaly (overprediction of turbulence production, see CFD5 study): this is the case for the k-ω/SST model (CFD6, CFD11, CFD12, CFD13, CFD14), non-linear/algebraic k-ε and k-ω models (CFD12, CFD13) and the rescaled V2F model (CFD15). This is not the case for the linear low-Re k-ε model used in CFD10. However, it must be pointed out again that these models predict massive separation, far from experiments.<br /> <br /> Low-Re Reynolds stress models seems to be able to reproduce (too late) reattachment on the slant part and the qualitatively correct wake structure (CFD13). However, this needs to be confirmed by further studies.<br /> <br /> LES (CFD9) is clearly able to reproduce the correct structure of the wake. However, using resolution down to the viscous sublayer is clearly unaffordable for the time being and the use of wall functions does not allow the correct reproduction of the boundary layer above the slant part.<br /> <br /> <br /> ==='''Recommendations for Future Work'''===<br /> <br /> '''Experiments:'''<br /> <br /> • Quantification of the large-scale unsteadiness and investigation of its role in the drag crisis<br /> <br /> <br /> <br /> '''CFD'''<br /> <br /> • The potential of low-Re RSM models must be further investigated<br /> <br /> • Wall-treatment for LES must be improved (see update below)<br /> <br /> • Since accounting for the near-wall region (low-Re RSM) and the large-scale unsteadiness (LES) have beneficial effects, the potential of accounting for both must be investigated: RANS/LES zonal coupling, RANS/LES hybrid models, Unsteady RANS, … (see update below)<br /> <br /> ==='''Update by F. R. Menter added in 2024'''===<br /> <br /> In the years between the ERCOFTAC workshop and today (2024) it was found that steady-state RANS models are not well suited for high accuracy CFD simulations of external automotive geometries. This is well reflected by the contributions to the [https://autocfd.eng.ox.ac.uk/ AutoCFD workshop], where a number of generic and semi-realistic automotive cases have been computed by numerous groups over the years. Most of the contributions to the workshop involve either hybrid RANS-LES or Wall-Function LES applications. This trend increased by the availability of low-cost GPU-based computing power and the corresponding CFD codes, utilizing this advanced hardware. By-and-large an order of magnitude increase in computer-power is achieved at the same cost relative to CPU based clusters. This allows for the wide-spread application of Scale-Resolving Simulations (SRS) to automotive design. <br /> <br /> Even with this increase in computing power, the routine application of wall-resolved LES is not a practical option for engineering simulations. The most popular SRS methods are therefore global hybrid models like [https://link.springer.com/article/10.1007/s10494-011-9378-4 DDES] or [https://link.springer.com/chapter/10.1007/978-3-319-70031-1_3 SBES]. In these models, the attached boundary layer is covered by the RANS model whereas separated regions are automatically detected by the shielding functions and the models switch to LES. The SBES model is an improved version of the DDES model with better boundary layer shielding and more pronounced RANS-LES switching capabilities. The success of such methods depends both on the capability of the underlying RANS model to accurately predict separation lines as well as on the switching characteristics of the hybrid model. The alternative is to apply LES over the entire car, typically using a wall-model, either as a classical wall-function or a thin RANS layer near the wall to reduce resolution requirements. It is important to notice that the usage of LES on under-resolved meshes can also compromise the accuracy of separation onset predictions. While requiring a higher resolution of the boundary layer, the advantage of LES versus hybrid models is the ‘seamless’ transition between attached and separated flow regions (no model switch). <br /> <br /> At the current point, it is not obvious which of these SRS approaches will gain the upper hand. Most likely, both approaches will be applied to provide the design engineer with a set of tools, with a variation in cost/performance ratio to be used during different phases of the design process. It is also likely that tunable RANS models (e.g. like the GEKO model by [https://www.researchgate.net/publication/336105262_Development_of_a_Generalized_K-o_Two-Equation_Turbulence_Model Menter et al. 2020]) or models based on machine learning) can get back into the mix for quick initial design studies. <br /> <br /> As a final comment, it should be noted that the Ahmed car body with slant angle of 25° is a highly sensitive test case due to its geometric proximity to a topological change of the flow. Even small modifications in model formulation, numerical settings or grid resolution can ‘flip’ the flow from one topology to another. Some of the sensitivities observed for that test case will therefore not necessarily be present in more realistic automotive configurations. <br /> <br /> =='''References'''==<br /> Menter, F. R., Matyushenko A., Lechner R.: Development of a generalized k-omega two-equation turbulence model. In Dillmann A. et al(eds) , New Results in Numerical and Experimental Fluid Mechanics XII, pp. 101-109. Springer (2020) <br /> <br /> <br /> © copyright ERCOFTAC 2004<br /> <br /> <br /> ----<br /> <br /> ''Contributors: Remi Manceau; Jean-Paul Bonnet - Université de Poitiers. Update (2024) F.R.Menter, ANSYS Germany'', <br /> <br /> <br /> {{AC|front=AC 1-05|description=Description_AC1-05|testdata=Test Data_AC1-05|cfdsimulations=CFD Simulations_AC1-05|evaluation=Evaluation_AC1-05|qualityreview=Quality Review_AC1-05|bestpractice=Best Practice Advice_AC1-05|relatedUFRs=Related UFRs_AC1-05}}</div> Mike https://kbwiki.ercoftac.org/w/index.php?title=Evaluation_AC1-05&diff=45206 Evaluation AC1-05 2024-02-09T10:59:41Z <p>Mike: </p> <hr /> <div>{{AC|front=AC 1-05|description=Description_AC1-05|testdata=Test Data_AC1-05|cfdsimulations=CFD Simulations_AC1-05|evaluation=Evaluation_AC1-05|qualityreview=Quality Review_AC1-05|bestpractice=Best Practice Advice_AC1-05|relatedUFRs=Related UFRs_AC1-05}}<br /> <br /> ='''Ahmed body'''=<br /> <br /> '''Application Challenge 1-05''' © copyright ERCOFTAC 2004<br /> <br /> <br /> <br /> =='''Comparison of Test data and CFD'''==<br /> <br /> Experiments provide very detailed data that offer a particularly difficult challenge to CFD. They showed that the drag crisis experienced by the body around 25°-30° is related to a dramatic change of the structure of the wake. The low-drag configuration (35°) consists in a massively separated wake, which is quasi-2D, while the high-drag configuration (25°) consists in a very complex, 3D wake structure, with a reattachment of the flow on the slant part and a strong interaction of the bubble with intense corner vortices, which are very energy-consuming.<br /> <br /> EXP1 shows that fixing a splitter plate in the wake of the body, in the symmetry plane, forces the flow to turn back to the low drag configuration (massively separated wake). The mechanism underlying these phenomena is not clear, but it could be due to the fact that the splitter plate counteracts a flapping of the wake in the span-wise direction. Therefore, there are some evidences that large-scale unsteadiness of the wake could play a crucial role in the wake structure transition. It could also explain high levels of turbulent stresses above the slant part that are very difficult to predict with steady-state RANS calculations.<br /> <br /> It appears from all the CFD results that the wake structure of the low drag configurations (35°) is correctly reproduced by all the turbulence models tested. The correct trend of the drag coefficient with the slant angle is correctly reproduced (CFD1), but the correct level is not found. In general, since the wake structure is correct, the pressure levels on the slant part are realistic, but the exact pressure repartition on the slant part and the vertical base are hardly reproduced.<br /> <br /> <br /> Concerning the high-drag configuration (25°), the great majority of the CFD computations were not able to reproduce the complex, 3D structure of the wake: a massively separated wake is obtained, which shows that the wake structure transition is missed. The number of computation and the variety of numerical schemes and meshes give many indications that the main issue is not numerical, but linked to the physical modeling: turbulence model and steady-state strategy. It appears that only two types of modeling are able to reproduce the structure of the wake: LES (CFD9) and low-Reynolds number Reynolds stress model (CFD13). It should indicate that the large-scale unsteadiness of the wake must be resolved (the potential of URANS has not been investigated extensively yet) or, alternatively, the absence of large-scale unsteadiness resolution must be compensated by a very refined turbulence modeling (Reynolds stress transport equations and integration down to the wall). However, these partial conclusions are only based on one LES and one low-Re RSM computation. Additional studies are necessary to confirm these favorable conclusions.<br /> <br /> <br /> The paper of Florian Menter extracted from the Proceedings of the 10th ERCOFTAC IAHR Workshop (http://www.ercoftac.nl/workshop10/index.html) with permission, gives a further comparison of experimental and CFD results, including various figures. This paper can be obtained by clicking [{{filepath:Ahmed.florian.menter.pdf}} here].<br /> <br /> ==='''Update added in 2024 by F.R. Menter'''===<br /> <br /> Since the ERCOFTAC workshops, simulations have progressed with an increased focus on Scale-Resolving Simulations. The simulations fall in two categories: Hybrid RANS-LES model and pure LES model simulations. Hybrid RANS-LES methods seem well suited for the Ahmed 25° car. They avoid the high cost of LES near the wall of the attached boundary layers. The ability of such models to predict the complex flow topology for the 25° case depends however on the ability of the underlying RANS model to predict separation from the slant onset. For a discussion of hybrid methods with application to this current test case see e.g. Guilminesau et al. (2020), Ekman et al. (2020).<br /> <br /> The application of LES to the 25° case proved surprisingly difficult. Up to the publication by Menter et al (2024) no LES with acceptable accuracy for the exp. Reynolds number has been achieved. For a review of LES studies see Menter et al (2024). Of special interest is that simulations at artificially reduced Reynolds number were able to predict the correct flow topology with separation and reattachment on the slant, even on coarse grids. However, at the exp. Reynolds number, the simulations showed a similar behavior to RANS models. In one set of simulations, the flow stayed attached (like with k- type models) and in another set, the flow stalled (like with SST type models). The authors in Menter et al (2024) confirmed this observation, even for much finer meshes than used previously (e.g. a 560 million block-structured hexahedral mesh resulted in fully attached flow). Only after turning to Octree meshes, which allow a three-dimensional refinement towards the wall, could a sufficient resolution of the boundary layer be achieved to allow a reliable prediction of separation and reattachment on the slant. The following pictures are taken from Menter et al (2024).<br /> <br /> {|align=&quot;center&quot;<br /> |[[Image:Ac1_05_figure_2.png|600px|center|]]<br /> |-<br /> |''Figure 2:'' Zoom of Octree meshes O1 and O2 near the roof-slant intersection. <br /> |}<br /> <br /> {|align=&quot;center&quot;<br /> |[[Image:Ac1_05_figure_3a.png|600px|center|]]<br /> |-<br /> |[[Image:Ac1_05_figure_3b.png|600px|center|]]<br /> |-<br /> |''Figure 3:'' Flow structure on roof-center plane for WALE O1(top) and WALE O2 (bottom) meshes showing contours of vorticity. <br /> |}<br /> <br /> {|align=&quot;center&quot;<br /> |[[Image:Ac1_05_figure_4.png|600px|center|]]<br /> |-<br /> |''Figure 4:'' Wall shear stress on the roof-center plane for WALE- O2 and WALE- O1 in comparison with SBES/RANS solution. <br /> |}<br /> <br /> <br /> Fig. 2 shows two Octree meshes near the roof-slant onset of the Ahmed car. The coarser mesh has 230 million and the refined mesh has 320 million cells. Both grids are formally of sufficient near-wall resolution for a wall-resolved LES (with ∆x^+=∆z^+≈35,∆y^+=1 in streamwise, spanwise and wall-normal direction respectively). However, the 320 million cell mesh (O1) has an overall finer mesh in the central part of the boundary layer. This results in a resolution of finer turbulence structures in the roof boundary layer as seen in Fig.3. The improved resolution brings the LES closer to the wall shear stress distribution (Cf) of the SST/SBES model which can serve as a reliable reference for the zero-pressure gradient flow in that region (Fig.4).<br /> <br /> <br /> {|align=&quot;center&quot;<br /> |[[Image:Ac1_05_figure_5.png|600px|center|]]<br /> |-<br /> |''Figure 5:'' Velocity profiles in center plane for WRLES on O1 and O2 grids, compared to experimental data. <br /> |}<br /> <br /> {|align=&quot;center&quot;<br /> |[[Image:Ac1_05_figure_6.png|600px|center|]]<br /> |-<br /> |''Figure 6:'' Stress profiles for streamwise coordinate in center plane for WRLES on O1 and O2 grids, compared to experimental data. <br /> |}<br /> <br /> Both meshes produce highly accurate representations of the separation bubble on the slant as seen from the velocity profiles in Fig. 5. Included in the figure is also a simulation on the O1 mesh where the WALE model was deactivated in the entire domain, which resulted in an even slightly better agreement with the experimental data. Fig. 6 shows the corresponding profiles for the streamwise stress component, which are again in good agreement with the experimental data, in contrast to RANS models which strongly underpredicted the stress level. While there are acceptable velocity profile results available for hybrid models e.g. Guilmineau et al. (2020), also none of these simulations captures the correct stress-level, especially just downstream of the slant onset. This points to a high consistency of the depicted LES simulations. <br /> <br /> <br /> {|align=&quot;center&quot;<br /> |[[Image:Ac1_05_figure_7a.png|400px]][[Image:Ac1_05_figure_7b.png|400px]]<br /> |-<br /> |''Figure 7:'' : Flow topology on slant of Ahmed car. Left: experimental oil flow (from Ahmed et al 1984). Right: Octree O1 – no model simulation. <br /> |}<br /> <br /> Figure 7 shows the flow topology for the O1 (no model) simulation compared to the experimental oil flow. As expected from the close agreement in the velocity profiles, the agreement in the flow pattern is also very close. <br /> <br /> <br /> {|align=&quot;center&quot;<br /> |[[Image:Ac1_05_figure_8.png|600px|center|]]<br /> |-<br /> |''Figure 8:'' Q-criterion plots for Octree O1 no model solution. Large picture has &lt;math&gt;Q=5 \cdot 10^6s^{-2}&lt;/math&gt; and smaller picture has &lt;math&gt;Q=1 \cdot 10^8s^{-2}&lt;/math&gt;. <br /> |}<br /> <br /> Finally, Figure 8 shows the resolved turbulence structures using the Q-criterion with a zoom to the slant onset region for the O1 mesh. As seen, this mesh allows for a very fine resolution of the turbulence which is necessary to accurately capture flow reattachment. <br /> <br /> =='''References'''==<br /> Ekman , P., Wieser, D., Virdung, T., Karlsson, M., Assessment of hybrid RANS-LES methods for accurate aerodynamic simulations. J. of wind Engg. And Industrial Aerodynamics, 206, (2020), 104301.<br /> <br /> Guilmineau E., Deng G.B., Leroyer A., Queutey P. Visonneau M., Wackers J., Assessment of hybrid RANS-LES formulations for flow simulation around the Ahmed body. Comput. Fluids 176, 302-319 (2018) <br /> <br /> Menter,F.R., Hüppe A., Flad D., Garburak, A. V., Matyushenko A.A., Stabnikov A.S., Large eddy simulations for the Ahmed car at 25° slant angle at different Teynolds numbers. Flow, Turbulence and Combustion, 112, 321-343, (2024).<br /> <br /> © copyright ERCOFTAC 2004<br /> <br /> <br /> ----<br /> <br /> ''Contributors: Remi Manceau; Jean-Paul Bonnet - Université de Poitiers. Update (2024) F.R.Menter, ANSYS Germany'', <br /> <br /> <br /> {{AC|front=AC 1-05|description=Description_AC1-05|testdata=Test Data_AC1-05|cfdsimulations=CFD Simulations_AC1-05|evaluation=Evaluation_AC1-05|qualityreview=Quality Review_AC1-05|bestpractice=Best Practice Advice_AC1-05|relatedUFRs=Related UFRs_AC1-05}}</div> Mike https://kbwiki.ercoftac.org/w/index.php?title=File:Ac1_05_figure_8.png&diff=45205 File:Ac1 05 figure 8.png 2024-02-09T09:58:53Z <p>Mike: </p> <hr /> <div></div> Mike https://kbwiki.ercoftac.org/w/index.php?title=File:Ac1_05_figure_7b.png&diff=45204 File:Ac1 05 figure 7b.png 2024-02-09T09:58:40Z <p>Mike: </p> <hr /> <div></div> Mike https://kbwiki.ercoftac.org/w/index.php?title=File:Ac1_05_figure_7a.png&diff=45203 File:Ac1 05 figure 7a.png 2024-02-09T09:58:27Z <p>Mike: </p> <hr /> <div></div> Mike https://kbwiki.ercoftac.org/w/index.php?title=File:Ac1_05_figure_6.png&diff=45202 File:Ac1 05 figure 6.png 2024-02-09T09:57:51Z <p>Mike: </p> <hr /> <div></div> Mike https://kbwiki.ercoftac.org/w/index.php?title=File:Ac1_05_figure_5.png&diff=45201 File:Ac1 05 figure 5.png 2024-02-09T09:57:39Z <p>Mike: </p> <hr /> <div></div> Mike https://kbwiki.ercoftac.org/w/index.php?title=File:Ac1_05_figure_4.png&diff=45200 File:Ac1 05 figure 4.png 2024-02-09T09:56:44Z <p>Mike: </p> <hr /> <div></div> Mike https://kbwiki.ercoftac.org/w/index.php?title=File:Ac1_05_figure_3b.png&diff=45199 File:Ac1 05 figure 3b.png 2024-02-09T09:56:27Z <p>Mike: </p> <hr /> <div></div> Mike https://kbwiki.ercoftac.org/w/index.php?title=File:Ac1_05_figure_3a.png&diff=45198 File:Ac1 05 figure 3a.png 2024-02-09T09:56:18Z <p>Mike: </p> <hr /> <div></div> Mike https://kbwiki.ercoftac.org/w/index.php?title=File:Ac1_05_figure_2.png&diff=45197 File:Ac1 05 figure 2.png 2024-02-09T09:56:06Z <p>Mike: </p> <hr /> <div></div> Mike https://kbwiki.ercoftac.org/w/index.php?title=CFD_Simulations_AC1-05&diff=45196 CFD Simulations AC1-05 2024-02-09T09:44:20Z <p>Mike: </p> <hr /> <div>{{AC|front=AC 1-05|description=Description_AC1-05|testdata=Test Data_AC1-05|cfdsimulations=CFD Simulations_AC1-05|evaluation=Evaluation_AC1-05|qualityreview=Quality Review_AC1-05|bestpractice=Best Practice Advice_AC1-05|relatedUFRs=Related UFRs_AC1-05}}<br /> <br /> ='''Ahmed body'''=<br /> <br /> '''Application Challenge 1-05''' © copyright ERCOFTAC 2004<br /> <br /> <br /> <br /> =='''Overview of CFD Simulations'''==<br /> <br /> CFD simulations have developed rapidly during the writing of the present document, during the MOVA consortium and in the frame of the 9th and 10th ERCOFTAC-IAHR Workshop on Refined Turbulence Modeling organized in Darmstad, Germany and Poitiers, France, in 2001 and 2002, respectively. These workshops were organized under the auspices of the Special Interest Group 15 on Turbulence Modeling of ERCOFTAC. The proceedings of the 10th ERCOFTAC-IAHR Workshop can be found at:<br /> <br /> [http://www.ercoftac.nl/workshop10/index.html http://www.ercoftac.nl/workshop10/index.html]<br /> <br /> For the 10th ERCOFTAC-IAHR Workshop, several recommendations were made to the groups participating in the CFD calculations. Among them the recommendation to extend the computational domain up to 5 times the car length downstream of the body, and the possibility to omit the stilts.<br /> <br /> Many of the CFD results are considered by the authors themselves as preliminary computations and were therefore not inserted into the knowledge base.<br /> <br /> The geometry is simple enough to be satisfactorily represented.<br /> <br /> =='''Simulation Case CFD1'''==<br /> <br /> ==='''Solution strategy CFD1'''===<br /> <br /> RANS modelling.<br /> <br /> Commercial FLUENT 4.2 code, based on unstructured finite volume discretization.<br /> <br /> Reynolds number: 4.29x106 (see EXP1). Steady state computation.<br /> <br /> The slant angle is varied from 0 to 50 degrees.<br /> <br /> <br /> ==='''Computational Domain CFD1'''===<br /> <br /> Symmetry is used to compute half the domain.<br /> <br /> Domain: [-3L;5L]x[0;2L]x[0;2L]<br /> <br /> Mesh : 450,000 cells<br /> <br /> Approximate value of y+ on solid surfaces : 30.<br /> <br /> <br /> ==='''Boundary Conditions CFD1'''===<br /> <br /> Inlet: turbulence level 0.5% with a mixing length of 5x10-3m.<br /> <br /> Outlet: constant pressure.<br /> <br /> Solid boundaries: wall functions<br /> <br /> Symmetry plane: symmetry<br /> <br /> Other boundaries: no details<br /> <br /> <br /> ==='''Application of Physical Models CFD1'''===<br /> <br /> Standard K-ε model with standard wall functions.<br /> <br /> <br /> ==='''Numerical Accuracy CFD1'''===<br /> <br /> Mesh refinement is performed until the drag reaches a constant value.<br /> <br /> Convection scheme : 2nd order.<br /> <br /> <br /> ==='''CFD Results CFD1'''===<br /> <br /> Friction lines, pressure iso-contours at the model surface, velocity vector fields, drag coefficient.<br /> <br /> =='''References CFD1'''==<br /> <br /> '''Modelling of stationnary three-dimensional separated flows around an Ahmed reference model.'''<br /> <br /> P. Gilliéron, F. Chometon, ESAIM proc., vol 7, 173-182, 1999<br /> <br /> <br /> =='''Simulation Case CFD2'''==<br /> <br /> ==='''Solution strategy CFD2'''===<br /> <br /> RANS modeling.<br /> <br /> Commercial FLUENT 5 code based on unstructured finite volume discretization.<br /> <br /> Reynolds number: 4.29x106 (see EXP1). Steady state computation.<br /> <br /> Slant angle: 30°.<br /> <br /> ==='''Computational Domain CFD2'''===<br /> <br /> Symmetry is used to compute half the domain. Stilts are included.<br /> <br /> Domain: no details.<br /> <br /> Mesh : 704,000 cells.<br /> <br /> y+ at the first grid point from the wall of order of 50 - 350.<br /> <br /> ==='''Boundary Conditions CFD2'''===<br /> <br /> No details.<br /> <br /> ==='''Application of Physical Models CFD2'''===<br /> <br /> - Standard k-ε model with non-equilibrium wall functions.<br /> <br /> - RSM (no details) with non-equilibrium wall functions.<br /> <br /> ==='''Numerical Accuracy CFD2'''===<br /> <br /> No details.<br /> <br /> ==='''CFD Results CFD2'''===<br /> <br /> Pathlines and velocities.<br /> <br /> Aerodynamic drag coefficient.<br /> <br /> =='''References CFD2'''==<br /> <br /> Advances in external-aero simulation of ground vehicles using the steady RANS equation.<br /> <br /> Makowski F.T and Kim S.E., SAE Conf 2000-01-0484<br /> <br /> <br /> =='''Simulation Case CFD3'''==<br /> <br /> ==='''Solution strategy CFD3'''===<br /> <br /> '''Large-eddy simulation.'''<br /> <br /> In house code PRICELES, based on unstructured second-order finite-element discretization.<br /> <br /> Reynolds number= 4.29 x106<br /> <br /> Slant angle: 28°.<br /> <br /> ==='''Computational Domain CFD3'''===<br /> <br /> Domain: [-3L;5L]x[-L;L]x[-LxL] (the ground plate is NOT included: the body is suspended in the middle of the domain).<br /> <br /> Mesh: 1.6x106 cells.<br /> <br /> y+ at the first grid point from the wall is about 80 (averaged value).<br /> <br /> ==='''Boundary Conditions CFD3'''===<br /> <br /> Inlet: constant velocity.<br /> <br /> Outlet: constant pressure conditions.<br /> <br /> Solid boundaries: wall functions<br /> <br /> Other boundaries : symmetry.<br /> <br /> ==='''Application of Physical Models CFD3'''===<br /> <br /> Sub-grid model: standard Smagorinsky.<br /> <br /> ==='''Numerical Accuracy CFD3'''===<br /> <br /> Second-order convection scheme and time marching (CFL number=3).<br /> <br /> ==='''CFD Results CFD3'''===<br /> <br /> '''Pressure, pressure coef., velocity, drag coef, Q-criterion contours, vorticity.'''<br /> <br /> =='''References CFD3'''==<br /> <br /> Large eddy simulation of an Ahmed reference model.<br /> <br /> R.J.A. Howard, M. Pourquie.<br /> <br /> Journal of Turbulence, 2002<br /> <br /> <br /> =='''Simulation Case CFD4'''==<br /> <br /> ==='''Solution strategy CFD4'''===<br /> <br /> RANS modelling.<br /> <br /> Commercial AVL SWIFT code, based on unstructured finite volume discretization.<br /> <br /> Reynolds number: 2.78x106 (see EXP2). Steady state computation.<br /> <br /> Slant angle: 25° and 35°.<br /> <br /> ==='''Computational Domain CFD4'''===<br /> <br /> Symmetry is used to compute half the domain.<br /> <br /> Domain: Inlet at -1.5L. No other details.<br /> <br /> Mesh : 530,000 cells.<br /> <br /> y+ on solid surfaces &lt; 100.<br /> <br /> ==='''Boundary Conditions CFD4'''===<br /> <br /> Inlet: interpolated experimental profile at –1.4L used at –1.5L.<br /> <br /> Solid boundaries: wall functions<br /> <br /> Symmetry plane: symmetry<br /> <br /> Other boundaries: no details<br /> <br /> ==='''Application of Physical Models CFD4'''===<br /> <br /> - Standard k-ε model with standard wall functions.<br /> <br /> - SSG Reynolds stress model with standard wall functions<br /> <br /> - Hybrid k-ε/Reynolds stress model (coefficient Cm of the k-ε model obtained from Reynolds stress transport equations) with standard wall functions<br /> <br /> ==='''Numerical Accuracy CFD4'''===<br /> <br /> Grid sensitivity study.<br /> <br /> Study of the influence of the convection scheme.<br /> <br /> ==='''CFD Results CFD4'''===<br /> <br /> Cp, velocity profiles in the boundary layer over the slant part.<br /> <br /> =='''References CFD4'''==<br /> <br /> B. Basara, S. Jakirlic, Flow Around a simplified car body (Ahmed body) : description of numerical methodology, in : S. Jakirlic, R. Jester-Zürker, C. Tropea, editors, 9th ERCOFTAC/IAHR/COST Workshop on Refined Turbulence Modelling, Oct. 4-5, 2001, Darmstadt University of Technology, Germany.<br /> <br /> <br /> =='''Simulation Case CFD5'''==<br /> <br /> =='''Solution strategy CFD5'''==<br /> <br /> RANS modelling.<br /> <br /> In-house code Saturne, based on unstructured finite volume discretization.<br /> <br /> Reynolds number: 2.78x106 (see EXP2). Steady state computation.<br /> <br /> Slant angle: 25° and 35°.<br /> <br /> ==='''Computational Domain CFD5'''===<br /> <br /> Full body (no symmetry used)<br /> <br /> Domain: no details<br /> <br /> Mesh : 300,000 cells<br /> <br /> y+ on solid surfaces : no details.<br /> <br /> ==='''Boundary Conditions CFD5'''===<br /> <br /> Inlet: no details.<br /> <br /> Solid boundaries: wall functions<br /> <br /> Other boundaries: no details<br /> <br /> ==='''Application of Physical Models CFD5'''===<br /> <br /> - Standard k-ε model with standard wall functions<br /> <br /> - Launder, Reece, Rodi (IP) Reynolds stress model with standard wall functions<br /> <br /> - Linearized production k-ε model with standard wall functions<br /> <br /> <br /> ==='''Numerical Accuracy CFD5'''===<br /> <br /> Convection scheme : 80% central differencing (2nd order), 20% upwind differencing (1st order).<br /> <br /> ==='''CFD Results CFD5'''===<br /> <br /> Cp, velocity profiles in the boundary layer over the slant part.<br /> <br /> Vector plots, turbulent energy contours, streamlines.<br /> <br /> =='''References CFD5'''==<br /> <br /> S. Tekam, D. Laurence, T. Buchal, Flow around the Ahmed body, in : S. Jakirlic, R. Jester-Zürker, C. Tropea, editors, 9th ERCOFTAC/ IAHR/ COST Workshop on Refined Turbulence Modelling, Oct. 4-5, 2001, Darmstadt University of Technology, Germany.<br /> <br /> <br /> =='''Simulation Case CFD6'''==<br /> <br /> ==='''Solution strategy CFD6'''===<br /> <br /> RANS modelling.<br /> <br /> Commercial FLUENT code, based on unstructured finite volume discretization.<br /> <br /> Reynolds number: 2.78x106 (see EXP2). Steady state computation.<br /> <br /> Slant angle: 25°.<br /> <br /> ==='''Computational Domain CFD6'''===<br /> <br /> Domain: no details<br /> <br /> Mesh : 2.3x106 cells<br /> <br /> y+ on solid surfaces : no details<br /> <br /> ==='''Boundary Conditions CFD6'''===<br /> <br /> Solid boundaries:<br /> <br /> - non-equilibrium wall functions for the k-ε model<br /> <br /> - no slip walls for the SST model<br /> <br /> <br /> <br /> Inlet, outlet and other boundaries: no details<br /> <br /> ==='''Application of Physical Models CFD6'''===<br /> <br /> - Realizable k-ε model with non-equilibrium wall functions<br /> <br /> - SST model<br /> <br /> ==='''Numerical Accuracy CFD6'''===<br /> <br /> No details<br /> <br /> ==='''CFD Results CFD6'''===<br /> <br /> Cp, velocity profiles in the boundary layer over the slant part.<br /> <br /> =='''References CFD6'''==<br /> <br /> M. Lanfrit, M. Braun, D. Cokljat, Contribution to case 9.4: Ahmed body, in : S. Jakirlic, R. Jester-Zürker, C. Tropea, editors, 9th ERCOFTAC/ IAHR/ COST Workshop on Refined Turbulence Modelling, Oct. 4-5, 2001, Darmstadt University of Technology, Germany.<br /> <br /> <br /> =='''Simulation Case CFD7'''==<br /> <br /> ==='''Solution strategy CFD7'''===<br /> <br /> RANS modelling in unsteady mode.<br /> <br /> In-house X-Stream code, based on finite volume solver for multi block structured non-orthogonal, curvilinear grid with collocated data arrangement. The convection terms are discretized using hybrid scheme with more than 60% central differencing. The diffusion terms are approximated with central differences. The SIMPLE method is used for the pressure-velocity coupling.<br /> <br /> Reynolds number: 2.78x106 (see EXP2).<br /> <br /> Slant angle: 35°<br /> <br /> ==='''Computational Domain CFD7'''===<br /> <br /> Full body (no symmetry condition used).<br /> <br /> Domain: [-2L;5L]x[-1.2;1.2L]x[0;1.3L]<br /> <br /> 9th ERCOFTAC workshop: 500,000 cells<br /> <br /> 10th ERCOFTAC workshop: 2 meshes: 490,000 and 820,000 cells (fine mesh used for the k-ε model only)<br /> <br /> Approximate value of y+ on solid surfaces:<br /> <br /> - 9th workshop: 60<br /> <br /> - 10th workshop: 17 (coarse mesh) and 11 (fine mesh).<br /> <br /> ==='''Boundary Conditions CFD7'''===<br /> <br /> Inlet: turbulence intensity=2,5%<br /> <br /> Solid boundaries: wall functions<br /> <br /> Outlet: no details<br /> <br /> Other boundaries: no details<br /> <br /> ==='''Application of Physical Models CFD7'''===<br /> <br /> 9th ERCOFTAC workshop:<br /> <br /> - Standard k-ε model with standard wall functions<br /> <br /> - SSG Reynolds stress model with standard wall functions<br /> <br /> - SSS Reynolds stress model with non-equilibrium wall functions<br /> <br /> - V2F model with wall functions<br /> <br /> - Elliptic blending model (Reynolds stress model) with wall functions<br /> <br /> <br /> <br /> 10th ERCOFTAC workshop:<br /> <br /> - Standard k-ε model with wall functions<br /> <br /> - V2F model with wall functions<br /> <br /> - SSG Reynolds stress model with modified ε equation (Hanjalic, Jakirlic) and standard wall functions<br /> <br /> ==='''Numerical Accuracy CFD7'''===<br /> <br /> Convection scheme : 60% 2nd order central differencing, 40% 1st order upwind differencing.<br /> <br /> ==='''CFD Results CFD7'''===<br /> <br /> Cp contours on the slant part, velocity profiles in the boundary layer over the slant part, vectors plots in 13 planes (see EXP2).<br /> <br /> ==''References CFD7'''==<br /> <br /> O. Ouhlous, W. Khier, Y. Liu, K. Hanjalic, in: S. Jakirlic, R. Jester-Zürker, C. Tropea, editors, 9th ERCOFTAC/ IAHR/ COST Workshop on Refined Turbulence Modelling, Oct. 4-5, 2001, Darmstadt University of Technology, Germany.<br /> <br /> <br /> <br /> M. Hadziabdic, K. Hanjalic, W. Khier, Y. Liu, O. Ouhlous, Flow around a simplified car body (Ahmed car model), in: R. Manceau, J.-P. Bonnet, editors, 10th ERCOFTAC (SIG-15)/IAHR/QNET-CFD Workshop on Refined Turbulence Modelling, Oct. 10-11, 2002, Laboratoire d’études aérodynamiques, UMR CNRS 6609, Université de Poitiers, France.<br /> <br /> <br /> =='''Simulation Case CFD8'''==<br /> <br /> ==='''Solution strategy CFD8'''===<br /> <br /> RANS modelling.<br /> <br /> In-house code STREAM, which is a finite volume solver which uses a structured, non-orthogonal curvilinear, multi block grid and a fully collocated arrangement. The SIMPLE pressure correction method and Rie &amp; Chow interpolation are used to prevent unrealistic pressure fluctuations. The convection terms are discretized using an upwind scheme or a TVD scheme based on the third-order QUICK scheme.<br /> <br /> Reynolds number: 2.78x106 (see EXP2). Steady state computation.<br /> <br /> Slant angle: 25° and 35°.<br /> <br /> ==='''Computational Domain CFD8'''===<br /> <br /> Symmetry is used to compute half the domain. Stilts not included.<br /> <br /> Domain: [-2L;4L]x[0;L]x[0;L]<br /> <br /> Mesh : 300,000 cells<br /> <br /> Approximate value of y+ on solid surfaces : between 55 and 550.<br /> <br /> ==='''Boundary Conditions CFD8'''===<br /> <br /> Inlet:<br /> <br /> - U=38.51 m/s (based on the experimental profile at –1.4L in order to account for the flow deceleration in front of the body)<br /> <br /> - K=6.58x10-3 m2 s-2<br /> <br /> - nt/n=10 (influence tested)<br /> <br /> <br /> <br /> Outflow: zero gradients for all variables<br /> <br /> Solid boundaries: wall functions<br /> <br /> Symmetry plane: symmetry<br /> <br /> Other boundaries: symmetry<br /> <br /> ==='''Application of Physical Models CFD8'''===<br /> <br /> - Standard k-ε model with Yap correction and SCL wall functions (see below)<br /> <br /> - Standard k-ε model with Yap correction and UMIST-N wall functions<br /> <br /> - Linear realizable k-ε model with SCL wall functions<br /> <br /> - Linear realizable k-ε model with UMIST-A wall functions<br /> <br /> - Nonlinear k-ε model (Craft et al.) with SCL wall functions<br /> <br /> - Nonlinear k-ε model (Craft et al.) with UMIST-A wall functions<br /> <br /> <br /> <br /> Wall functions:<br /> <br /> - SCL = Simplified Chieng and Launder<br /> <br /> - UMIST-A = UMIST Analytical<br /> <br /> - UMIST-N = UMIST Numerical<br /> <br /> ==='''Numerical Accuracy CFD8'''===<br /> <br /> Convection scheme : 3rd order Quick scheme (UMIST) or 1st order upwind scheme in case of numerical instability.<br /> <br /> Tests were made to assess iteration convergence. Some unsteady calculations were made too. A coarser grid was used to obtain some information on grid dependency.<br /> <br /> ==='''CFD Results CFD8'''===<br /> <br /> Cp contours on the slant part, velocity profiles in the boundary layer over the slant part, vectors plots in 13 planes (see EXP2).<br /> <br /> =='''References CFD8'''==<br /> <br /> T.J. Craft, S.E. Gant, H. Iacovides, B.E. Launder, C.M.E. Robinson, Computational methods applied to the study of flow around a simplified “Ahmed” car body, in: R. Manceau, J.-P. Bonnet, editors, 10th ERCOFTAC (SIG-15)/IAHR/QNET-CFD Workshop on Refined Turbulence Modelling, Oct. 10-11, 2002, Laboratoire d’études aérodynamiques, UMR CNRS 6609, Université de Poitiers, France.<br /> <br /> <br /> =='''Simulation Case CFD9'''==<br /> <br /> ==='''Solution strategy CFD9'''===<br /> <br /> LES.<br /> <br /> In-house code LESOCC2, based on block-structured finite volume discretization. A collocated cell arrangement was used employing the Rhie and Chow momentum interpolation procedure. The SIMPLE scheme was used for the pressure-velocity coupling, and the pressure correction equation was solved using the SIP method. Fluxes were discretized in space using a second order central difference scheme. The equations were integrated in time using a second order Runge Kutta scheme with an adaptive time step, employing a maximum CFL number of 0.6.<br /> <br /> Reynolds number: 2.78x106 (see EXP2).<br /> <br /> Slant angle: 25°.<br /> <br /> ==='''Computational Domain CFD9'''===<br /> <br /> Domain: [-2.2L;4.8L]x[-0.9L;0.9L]x[0;1.35L]. Ground plate and stilts included.<br /> <br /> Mesh :18.5x106 cells<br /> <br /> y+ on solid surfaces : no details<br /> <br /> ==='''Boundary Conditions CFD9'''===<br /> <br /> Inlet: constant velocity<br /> <br /> Outlet: convective outlet.<br /> <br /> Solid boundaries: wall functions<br /> <br /> Other boundaries: slip walls<br /> <br /> ==='''Application of Physical Models CFD9'''===<br /> <br /> Subgrid scale model: Smagorinky<br /> <br /> ==='''Numerical Accuracy CFD9'''===<br /> <br /> 2nd order convection scheme and time marching (CFL number &lt; 0.6)<br /> <br /> ==='''CFD Results CFD9'''===<br /> <br /> Cp contours on the slant part, velocity profiles in the boundary layer over the slant part, vectors plots in 13 planes (see EXP2).<br /> <br /> =='''References CFD9'''==<br /> <br /> C. Hinterberger, M. Garcia-Villalba, W. Rodi, Flow around a simplified car body. LES with wall functions, in: R. Manceau, J.-P. Bonnet, editors, 10th ERCOFTAC (SIG-15)/IAHR/QNET-CFD Workshop on Refined Turbulence Modelling, Oct. 10-11, 2002, Laboratoire d’études aérodynamiques, UMR CNRS 6609, Université de Poitiers, France.<br /> <br /> <br /> =='''Simulation Case CFD10'''==<br /> <br /> ==='''Solution strategy CFD10'''===<br /> <br /> RANS modelling.<br /> <br /> Commercial HEXANS CFD code, based on unstructured finite volume discretization. The convective fluxes are discretized using a centered scheme with 2nd and 4th order artificial dissipation. Diffusive fluxes are computed on pyramidal elements. The equations are integrated in time using the explicit Runge Kutta scheme. Local time stepping, multi grid and low-mach number preconditioning are used to accelerate the convergence to steady state. A mesh adaptation procedure is used in which the grid cells are refined by splitting it in 2, 4 or 8 subcells. The mesh adaptation is governed by criteria based on the flow physics, geometry or error estimates.<br /> <br /> Reynolds number: 2.78x106 (see EXP2). Steady state computation.<br /> <br /> Slant angle: 25°.<br /> <br /> ==='''Computational Domain CFD10'''===<br /> <br /> Symmetry is used to compute half the domain. Ground plate included, no stilts.<br /> <br /> Domain: [-2L;5L]x[0;0.9L]x[0;1.35L]<br /> <br /> Final Mesh : 815,000 cells<br /> <br /> Approximate value of y+ on solid surfaces : 1<br /> <br /> ==='''Boundary Conditions CFD10'''===<br /> <br /> Inflow: turbulence level 1%. nt/n = 1.<br /> <br /> Solid boundaries: no-slip walls<br /> <br /> Symmetry plane: symmetry<br /> <br /> Other boundaries: no details<br /> <br /> ==='''Application of Physical Models CFD10'''===<br /> <br /> Low-Reynolds number K-ε model (Yang-Shih).<br /> <br /> ==='''Numerical Accuracy CFD10'''===<br /> <br /> Mesh adaptation applied.<br /> <br /> Convection scheme : 2nd order.<br /> <br /> ==='''CFD Results CFD10'''===<br /> <br /> Cp contours on the slant part, velocity profiles in the boundary layer over the slant part, vectors plots in 13 planes (see EXP2).<br /> <br /> =='''References CFD10'''==<br /> <br /> B. Leonard, Ch. Hirsch, K. Kovalev, M. Elsden, K. Hillewaert, A. Patel, Flow around a simplified car body (Ahmed body), in: R. Manceau, J.-P. Bonnet, editors, 10th ERCOFTAC (SIG-15)/IAHR/QNET-CFD Workshop on Refined Turbulence Modelling, Oct. 10-11, 2002, Laboratoire d’études aérodynamiques, UMR CNRS 6609, Université de Poitiers, France.<br /> <br /> <br /> =='''Simulation Case CFD11'''==<br /> <br /> ==='''Solution strategy CFD11'''===<br /> <br /> RANS modelling.<br /> <br /> Commercial CFX-5 code, based on an unstructured, vertex based finite volume method. Co-located variables are used. The solver is second order accurate in space and time. The Rhie-Chow velocity pressure coupling is used. An implicit solver with algebraic multi grid is used to converge the equations to steady state.<br /> <br /> Reynolds number: 2.78x106 (see EXP2). Transient computation (steady solution obtained).<br /> <br /> Slant angle: 25° and 35°.<br /> <br /> ==='''Computational Domain CFD11'''===<br /> <br /> Symmetry is used to compute half the domain. No stilts included.<br /> <br /> Domain: [-3L;6L]x[0;0.9L]x[0;1.15L]<br /> <br /> The ground plate starts 2L in front of the body in order that the boundary layer approaching the body matches the experimental profile.<br /> <br /> Mesh : 2,5x106 cells<br /> <br /> Approximate value of y+ on solid surfaces : 1<br /> <br /> ==='''Boundary Conditions CFD11'''===<br /> <br /> Inlet: turbulence intensity=1%, nt/n=1.<br /> <br /> Solid boundaries:<br /> <br /> - SST model: no slip walls<br /> <br /> - Others: scalable wall functions<br /> <br /> Outlet: constant pressure<br /> <br /> Other boundaries: opening boundary conditions.<br /> <br /> ==='''Application of Physical Models CFD11'''===<br /> <br /> - Standard k-ε model with scalable wall functions<br /> <br /> - SST model<br /> <br /> - SSG Reynolds stress model with scalable wall functions<br /> <br /> ==='''Numerical Accuracy CFD11'''===<br /> <br /> Convection scheme: 2nd order.<br /> <br /> Studies of the influence of the following parameters are performed:<br /> <br /> Mesh refinement, formulation of the boundary conditions (opening vs. slip walls), advection scheme.<br /> <br /> ==='''CFD Results CFD11'''===<br /> <br /> The same quantities (except for triple correlations) as for experiment EXP2 are available in the Knowledge Base : results for the mean velocities U, V, W, Reynolds stresses [[Image:Image23.gif]] [[Image:Image24.gif]] [[Image:Image25.gif]] [[Image:Image26.gif]] [[Image:Image27.gif]] in some planes and profiles in the boundary layer above the slant part:<br /> <br /> <br /> <br /> <br /> '''k-epsilon model'''<br /> <br /> 25° slant angle:<br /> <br /> planes:<br /> &lt;span class=&quot;plainlinks&quot;&gt;[{{filepath:CFD11_KEPS_Ahmed_25_y=0.dat}} y=0]&lt;/span&gt;;<br /> &lt;span class=&quot;plainlinks&quot;&gt;[{{filepath:CFD11_KEPS_Ahmed_25_y=100.dat}} y=100]&lt;/span&gt;; <br /> &lt;span class=&quot;plainlinks&quot;&gt;[{{filepath:CFD11_KEPS_Ahmed_25_y=180.dat}} y=180]&lt;/span&gt;;<br /> <br /> &lt;span class=&quot;plainlinks&quot;&gt;[{{filepath:CFD11_KEPS_Ahmed_25_y=195.dat}} y=195]&lt;/span&gt;;<br /> &lt;span class=&quot;plainlinks&quot;&gt;[{{filepath:CFD11_KEPS_Ahmed_25_z=360.dat}} z=360]&lt;/span&gt;<br /> <br /> &lt;span class=&quot;plainlinks&quot;&gt;[{{filepath:CFD11_KEPS_Ahmed_25_x=-794.dat}} x=-794]&lt;/span&gt;;<br /> &lt;span class=&quot;plainlinks&quot;&gt;[{{filepath:CFD11_KEPS_Ahmed_25_x=-178.dat}} x=-178]&lt;/span&gt;;<br /> &lt;span class=&quot;plainlinks&quot;&gt;[{{filepath:CFD11_KEPS_Ahmed_25_x=-138.dat}} x=-138]&lt;/span&gt;;<br /> &lt;span class=&quot;plainlinks&quot;&gt;[{{filepath:CFD11_KEPS_Ahmed_25_x=-88.dat}} x=-88]&lt;/span&gt;;<br /> &lt;span class=&quot;plainlinks&quot;&gt;[{{filepath:CFD11_KEPS_Ahmed_25_x=-38.dat}} x=-38]&lt;/span&gt;;<br /> &lt;span class=&quot;plainlinks&quot;&gt;[{{filepath:CFD11_KEPS_Ahmed_25_x=0.dat}} x=0]&lt;/span&gt;;<br /> &lt;span class=&quot;plainlinks&quot;&gt;[{{filepath:CFD11_KEPS_Ahmed_25_x=80.dat}} x=80]&lt;/span&gt;;<br /> &lt;span class=&quot;plainlinks&quot;&gt;[{{filepath:CFD11_KEPS_Ahmed_25_x=200.dat}} x=200]&lt;/span&gt;;<br /> &lt;span class=&quot;plainlinks&quot;&gt;[{{filepath:CFD11_KEPS_Ahmed_25_x=500.dat}} x=500]&lt;/span&gt;<br /> <br /> profiles in the boundary layer:<br /> &lt;span class=&quot;plainlinks&quot;&gt;[{{filepath:CFD11_KEPS_Ahmed_25_BL_x=-243.dat}} x=-243]&lt;/span&gt;,<br /> &lt;span class=&quot;plainlinks&quot;&gt;[{{filepath:CFD11_KEPS_Ahmed_25_BL_x=-223.dat}} -223]&lt;/span&gt;,<br /> &lt;span class=&quot;plainlinks&quot;&gt;[{{filepath:CFD11_KEPS_Ahmed_25_BL_x=-203.dat}} -203]&lt;/span&gt;,<br /> &lt;span class=&quot;plainlinks&quot;&gt;[{{filepath:CFD11_KEPS_Ahmed_25_BL_x=-183.dat}} -183]&lt;/span&gt;,<br /> &lt;span class=&quot;plainlinks&quot;&gt;[{{filepath:CFD11_KEPS_Ahmed_25_BL_x=-163.dat}} -163]&lt;/span&gt;,<br /> &lt;span class=&quot;plainlinks&quot;&gt;[{{filepath:CFD11_KEPS_Ahmed_25_BL_x=-143.dat}} -143]&lt;/span&gt;,<br /> &lt;span class=&quot;plainlinks&quot;&gt;[{{filepath:CFD11_KEPS_Ahmed_25_BL_x=-123.dat}} -123]&lt;/span&gt;,<br /> &lt;span class=&quot;plainlinks&quot;&gt;[{{filepath:CFD11_KEPS_Ahmed_25_BL_x=-103.dat}} -103]&lt;/span&gt;,<br /> &lt;span class=&quot;plainlinks&quot;&gt;[{{filepath:CFD11_KEPS_Ahmed_25_BL_x=-83.dat}} -83]&lt;/span&gt;,<br /> &lt;span class=&quot;plainlinks&quot;&gt;[{{filepath:CFD11_KEPS_Ahmed_25_BL_x=-63.dat}} -63]&lt;/span&gt;,<br /> &lt;span class=&quot;plainlinks&quot;&gt;[{{filepath:CFD11_KEPS_Ahmed_25_BL_x=-43.dat}} -43]&lt;/span&gt;,<br /> &lt;span class=&quot;plainlinks&quot;&gt;[{{filepath:CFD11_KEPS_Ahmed_25_BL_x=-23.dat}} -23]&lt;/span&gt;,<br /> &lt;span class=&quot;plainlinks&quot;&gt;[{{filepath:CFD11_KEPS_Ahmed_25_BL_x=-3.dat}} -3]&lt;/span&gt;<br /> <br /> Pressure coefficients on the rear of the body:<br /> &lt;span class=&quot;plainlinks&quot;&gt;[{{filepath:CFD11_KEPS_Ahmed_25_Cp.dat}} Cp]&lt;/span&gt;<br /> <br /> <br /> <br /> 35° slant angle:<br /> <br /> planes:<br /> &lt;span class=&quot;plainlinks&quot;&gt;[{{filepath:CFD11_KEPS_Ahmed_35_y=0.dat}} y=0]&lt;/span&gt;;<br /> &lt;span class=&quot;plainlinks&quot;&gt;[{{filepath:CFD11_KEPS_Ahmed_35_y=100.dat}} y=100]&lt;/span&gt;; <br /> &lt;span class=&quot;plainlinks&quot;&gt;[{{filepath:CFD11_KEPS_Ahmed_35_y=180.dat}} y=180]&lt;/span&gt;;<br /> <br /> &lt;span class=&quot;plainlinks&quot;&gt;[{{filepath:CFD11_KEPS_Ahmed_35_y=195.dat}} y=195]&lt;/span&gt;;<br /> &lt;span class=&quot;plainlinks&quot;&gt;[{{filepath:CFD11_KEPS_Ahmed_35_z=360.dat}} z=360]&lt;/span&gt;<br /> <br /> &lt;span class=&quot;plainlinks&quot;&gt;[{{filepath:CFD11_KEPS_Ahmed_35_x=-794.dat}} x=-794]&lt;/span&gt;;<br /> &lt;span class=&quot;plainlinks&quot;&gt;[{{filepath:CFD11_KEPS_Ahmed_35_x=-178.dat}} x=-178]&lt;/span&gt;;<br /> &lt;span class=&quot;plainlinks&quot;&gt;[{{filepath:CFD11_KEPS_Ahmed_35_x=-138.dat}} x=-138]&lt;/span&gt;;<br /> &lt;span class=&quot;plainlinks&quot;&gt;[{{filepath:CFD11_KEPS_Ahmed_35_x=-88.dat}} x=-88]&lt;/span&gt;;<br /> &lt;span class=&quot;plainlinks&quot;&gt;[{{filepath:CFD11_KEPS_Ahmed_35_x=-38.dat}} x=-38]&lt;/span&gt;;<br /> &lt;span class=&quot;plainlinks&quot;&gt;[{{filepath:CFD11_KEPS_Ahmed_35_x=0.dat}} x=0]&lt;/span&gt;;<br /> &lt;span class=&quot;plainlinks&quot;&gt;[{{filepath:CFD11_KEPS_Ahmed_35_x=80.dat}} x=80]&lt;/span&gt;;<br /> &lt;span class=&quot;plainlinks&quot;&gt;[{{filepath:CFD11_KEPS_Ahmed_35_x=200.dat}} x=200]&lt;/span&gt;;<br /> &lt;span class=&quot;plainlinks&quot;&gt;[{{filepath:CFD11_KEPS_Ahmed_35_x=500.dat}} x=500]&lt;/span&gt;<br /> <br /> profiles in the boundary layer:<br /> &lt;span class=&quot;plainlinks&quot;&gt;[{{filepath:CFD11_KEPS_Ahmed_35_BL_x=-243.dat}} x=-243]&lt;/span&gt;,<br /> &lt;span class=&quot;plainlinks&quot;&gt;[{{filepath:CFD11_KEPS_Ahmed_35_BL_x=-223.dat}} -223]&lt;/span&gt;,<br /> &lt;span class=&quot;plainlinks&quot;&gt;[{{filepath:CFD11_KEPS_Ahmed_35_BL_x=-203.dat}} -203]&lt;/span&gt;,<br /> &lt;span class=&quot;plainlinks&quot;&gt;[{{filepath:CFD11_KEPS_Ahmed_35_BL_x=-183.dat}} -183]&lt;/span&gt;,<br /> &lt;span class=&quot;plainlinks&quot;&gt;[{{filepath:CFD11_KEPS_Ahmed_35_BL_x=-163.dat}} -163]&lt;/span&gt;,<br /> &lt;span class=&quot;plainlinks&quot;&gt;[{{filepath:CFD11_KEPS_Ahmed_35_BL_x=-143.dat}} -143]&lt;/span&gt;,<br /> &lt;span class=&quot;plainlinks&quot;&gt;[{{filepath:CFD11_KEPS_Ahmed_35_BL_x=-123.dat}} -123]&lt;/span&gt;,<br /> &lt;span class=&quot;plainlinks&quot;&gt;[{{filepath:CFD11_KEPS_Ahmed_35_BL_x=-103.dat}} -103]&lt;/span&gt;,<br /> &lt;span class=&quot;plainlinks&quot;&gt;[{{filepath:CFD11_KEPS_Ahmed_35_BL_x=-83.dat}} -83]&lt;/span&gt;,<br /> &lt;span class=&quot;plainlinks&quot;&gt;[{{filepath:CFD11_KEPS_Ahmed_35_BL_x=-63.dat}} -63]&lt;/span&gt;,<br /> &lt;span class=&quot;plainlinks&quot;&gt;[{{filepath:CFD11_KEPS_Ahmed_35_BL_x=-43.dat}} -43]&lt;/span&gt;,<br /> &lt;span class=&quot;plainlinks&quot;&gt;[{{filepath:CFD11_KEPS_Ahmed_35_BL_x=-23.dat}} -23]&lt;/span&gt;,<br /> &lt;span class=&quot;plainlinks&quot;&gt;[{{filepath:CFD11_KEPS_Ahmed_35_BL_x=-3.dat}} -3]&lt;/span&gt;<br /> <br /> Pressure coefficients on the rear of the body:<br /> &lt;span class=&quot;plainlinks&quot;&gt;[{{filepath:CFD11_KEPS_Ahmed_35_Cp.dat}} Cp]&lt;/span&gt;<br /> <br /> <br /> <br /> '''SST model'''<br /> <br /> 25° slant angle:<br /> <br /> planes:<br /> &lt;span class=&quot;plainlinks&quot;&gt;[{{filepath:CFD11_SST_Ahmed_25_y=0.dat}} y=0]&lt;/span&gt;;<br /> &lt;span class=&quot;plainlinks&quot;&gt;[{{filepath:CFD11_SST_Ahmed_25_y=100.dat}} y=100]&lt;/span&gt;; <br /> &lt;span class=&quot;plainlinks&quot;&gt;[{{filepath:CFD11_SST_Ahmed_25_y=180.dat}} y=180]&lt;/span&gt;;<br /> <br /> &lt;span class=&quot;plainlinks&quot;&gt;[{{filepath:CFD11_SST_Ahmed_25_y=195.dat}} y=195]&lt;/span&gt;;<br /> &lt;span class=&quot;plainlinks&quot;&gt;[{{filepath:CFD11_SST_Ahmed_25_z=360.dat}} z=360]&lt;/span&gt;<br /> <br /> &lt;span class=&quot;plainlinks&quot;&gt;[{{filepath:CFD11_SST_Ahmed_25_x=-794.dat}} x=-794]&lt;/span&gt;;<br /> &lt;span class=&quot;plainlinks&quot;&gt;[{{filepath:CFD11_SST_Ahmed_25_x=-178.dat}} x=-178]&lt;/span&gt;;<br /> &lt;span class=&quot;plainlinks&quot;&gt;[{{filepath:CFD11_SST_Ahmed_25_x=-138.dat}} x=-138]&lt;/span&gt;;<br /> &lt;span class=&quot;plainlinks&quot;&gt;[{{filepath:CFD11_SST_Ahmed_25_x=-88.dat}} x=-88]&lt;/span&gt;;<br /> &lt;span class=&quot;plainlinks&quot;&gt;[{{filepath:CFD11_SST_Ahmed_25_x=-38.dat}} x=-38]&lt;/span&gt;;<br /> &lt;span class=&quot;plainlinks&quot;&gt;[{{filepath:CFD11_SST_Ahmed_25_x=0.dat}} x=0]&lt;/span&gt;;<br /> &lt;span class=&quot;plainlinks&quot;&gt;[{{filepath:CFD11_SST_Ahmed_25_x=80.dat}} x=80]&lt;/span&gt;;<br /> &lt;span class=&quot;plainlinks&quot;&gt;[{{filepath:CFD11_SST_Ahmed_25_x=200.dat}} x=200]&lt;/span&gt;;<br /> &lt;span class=&quot;plainlinks&quot;&gt;[{{filepath:CFD11_SST_Ahmed_25_x=500.dat}} x=500]&lt;/span&gt;<br /> <br /> profiles in the boundary layer:<br /> &lt;span class=&quot;plainlinks&quot;&gt;[{{filepath:CFD11_SST_Ahmed_25_BL_x=-243.dat}} x=-243]&lt;/span&gt;,<br /> &lt;span class=&quot;plainlinks&quot;&gt;[{{filepath:CFD11_SST_Ahmed_25_BL_x=-223.dat}} -223]&lt;/span&gt;,<br /> &lt;span class=&quot;plainlinks&quot;&gt;[{{filepath:CFD11_SST_Ahmed_25_BL_x=-203.dat}} -203]&lt;/span&gt;,<br /> &lt;span class=&quot;plainlinks&quot;&gt;[{{filepath:CFD11_SST_Ahmed_25_BL_x=-183.dat}} -183]&lt;/span&gt;,<br /> &lt;span class=&quot;plainlinks&quot;&gt;[{{filepath:CFD11_SST_Ahmed_25_BL_x=-163.dat}} -163]&lt;/span&gt;,<br /> &lt;span class=&quot;plainlinks&quot;&gt;[{{filepath:CFD11_SST_Ahmed_25_BL_x=-143.dat}} -143]&lt;/span&gt;,<br /> &lt;span class=&quot;plainlinks&quot;&gt;[{{filepath:CFD11_SST_Ahmed_25_BL_x=-123.dat}} -123]&lt;/span&gt;,<br /> -103,<br /> &lt;span class=&quot;plainlinks&quot;&gt;[{{filepath:CFD11_SST_Ahmed_25_BL_x=-83.dat}} -83]&lt;/span&gt;,<br /> &lt;span class=&quot;plainlinks&quot;&gt;[{{filepath:CFD11_SST_Ahmed_25_BL_x=-63.dat}} -63]&lt;/span&gt;,<br /> &lt;span class=&quot;plainlinks&quot;&gt;[{{filepath:CFD11_SST_Ahmed_25_BL_x=-43.dat}} -43]&lt;/span&gt;,<br /> &lt;span class=&quot;plainlinks&quot;&gt;[{{filepath:CFD11_SST_Ahmed_25_BL_x=-23.dat}} -23]&lt;/span&gt;,<br /> &lt;span class=&quot;plainlinks&quot;&gt;[{{filepath:CFD11_SST_Ahmed_25_BL_x=-3.dat}} -3]&lt;/span&gt;<br /> <br /> Pressure coefficients on the rear of the body:<br /> &lt;span class=&quot;plainlinks&quot;&gt;[{{filepath:CFD11_SST_Ahmed_25_Cp.dat}} Cp]&lt;/span&gt;<br /> <br /> <br /> <br /> 35° slant angle:<br /> planes:<br /> &lt;span class=&quot;plainlinks&quot;&gt;[{{filepath:CFD11_SST_Ahmed_35_y=0.dat}} y=0]&lt;/span&gt;;<br /> &lt;span class=&quot;plainlinks&quot;&gt;[{{filepath:CFD11_SST_Ahmed_35_y=100.dat}} y=100]&lt;/span&gt;; <br /> &lt;span class=&quot;plainlinks&quot;&gt;[{{filepath:CFD11_SST_Ahmed_35_y=180.dat}} y=180]&lt;/span&gt;;<br /> <br /> &lt;span class=&quot;plainlinks&quot;&gt;[{{filepath:CFD11_SST_Ahmed_35_y=195.dat}} y=195]&lt;/span&gt;;<br /> z=360<br /> <br /> &lt;span class=&quot;plainlinks&quot;&gt;[{{filepath:CFD11_SST_Ahmed_35_x=-178.dat}} x=-178]&lt;/span&gt;;<br /> &lt;span class=&quot;plainlinks&quot;&gt;[{{filepath:CFD11_SST_Ahmed_35_x=-138.dat}} x=-138]&lt;/span&gt;;<br /> &lt;span class=&quot;plainlinks&quot;&gt;[{{filepath:CFD11_SST_Ahmed_35_x=-88.dat}} x=-88]&lt;/span&gt;;<br /> &lt;span class=&quot;plainlinks&quot;&gt;[{{filepath:CFD11_SST_Ahmed_35_x=-38.dat}} x=-38]&lt;/span&gt;;<br /> &lt;span class=&quot;plainlinks&quot;&gt;[{{filepath:CFD11_SST_Ahmed_35_x=0.dat}} x=0]&lt;/span&gt;;<br /> &lt;span class=&quot;plainlinks&quot;&gt;[{{filepath:CFD11_SST_Ahmed_35_x=80.dat}} x=80]&lt;/span&gt;;<br /> &lt;span class=&quot;plainlinks&quot;&gt;[{{filepath:CFD11_SST_Ahmed_35_x=200.dat}} x=200]&lt;/span&gt;;<br /> &lt;span class=&quot;plainlinks&quot;&gt;[{{filepath:CFD11_SST_Ahmed_35_x=500.dat}} x=500]&lt;/span&gt;<br /> <br /> profiles in the boundary layer:<br /> &lt;span class=&quot;plainlinks&quot;&gt;[{{filepath:CFD11_SST_Ahmed_35_BL_x=-243.dat}} x=-243]&lt;/span&gt;,<br /> &lt;span class=&quot;plainlinks&quot;&gt;[{{filepath:CFD11_SST_Ahmed_35_BL_x=-223.dat}} -223]&lt;/span&gt;,<br /> &lt;span class=&quot;plainlinks&quot;&gt;[{{filepath:CFD11_SST_Ahmed_35_BL_x=-203.dat}} -203]&lt;/span&gt;,<br /> &lt;span class=&quot;plainlinks&quot;&gt;[{{filepath:CFD11_SST_Ahmed_35_BL_x=-183.dat}} -183]&lt;/span&gt;,<br /> &lt;span class=&quot;plainlinks&quot;&gt;[{{filepath:CFD11_SST_Ahmed_35_BL_x=-163.dat}} -163]&lt;/span&gt;,<br /> &lt;span class=&quot;plainlinks&quot;&gt;[{{filepath:CFD11_SST_Ahmed_35_BL_x=-143.dat}} -143]&lt;/span&gt;,<br /> &lt;span class=&quot;plainlinks&quot;&gt;[{{filepath:CFD11_SST_Ahmed_35_BL_x=-123.dat}} -123]&lt;/span&gt;,<br /> &lt;span class=&quot;plainlinks&quot;&gt;[{{filepath:CFD11_SST_Ahmed_35_BL_x=-103.dat}} -103]&lt;/span&gt;,<br /> &lt;span class=&quot;plainlinks&quot;&gt;[{{filepath:CFD11_SST_Ahmed_35_BL_x=-83.dat}} -83]&lt;/span&gt;,<br /> &lt;span class=&quot;plainlinks&quot;&gt;[{{filepath:CFD11_SST_Ahmed_35_BL_x=-63.dat}} -63]&lt;/span&gt;,<br /> &lt;span class=&quot;plainlinks&quot;&gt;[{{filepath:CFD11_SST_Ahmed_35_BL_x=-43.dat}} -43]&lt;/span&gt;,<br /> &lt;span class=&quot;plainlinks&quot;&gt;[{{filepath:CFD11_SST_Ahmed_35_BL_x=-23.dat}} -23]&lt;/span&gt;,<br /> &lt;span class=&quot;plainlinks&quot;&gt;[{{filepath:CFD11_SST_Ahmed_35_BL_x=-3.dat}} -3]&lt;/span&gt;<br /> <br /> Pressure coefficients on the rear of the body:<br /> &lt;span class=&quot;plainlinks&quot;&gt;[{{filepath:CFD11_SST_Ahmed_35_Cp.dat}} Cp]&lt;/span&gt;<br /> <br /> =='''References CFD11'''==<br /> <br /> L. Durand, M. Kuntz, F. Menter, Validation of CFX-5 for the Ahmed car body (synopsis), in: R. Manceau, J.-P. Bonnet, editors, 10th ERCOFTAC (SIG-15)/IAHR/QNET-CFD Workshop on Refined Turbulence Modelling, Oct. 10-11, 2002, Laboratoire d’études aérodynamiques, UMR CNRS 6609, Université de Poitiers, France.<br /> <br /> <br /> <br /> L. Durand, M. Kuntz, F. Menter, Validation of CFX-5 for the Ahmed car body, CFX Validation report (florian.menter@ansys.com)<br /> <br /> <br /> =='''Simulation Case CFD12'''==<br /> <br /> ==='''Solution strategy CFD12'''===<br /> <br /> RANS modelling.<br /> <br /> In-house code CFL3D, compressible flow solver employing multi block structured grids. An upwind finite volume formulation is used for the space discretization. An implicit approximate factorization method is used to integrate the equations in time. Local time stepping, grid sequencing, multi grid and low Mach number preconditioning are used to accelerate convergence to steady state.<br /> <br /> Reynolds number: 2.78x106 (see EXP2). Steady state computation.<br /> <br /> Slant angle: 25° and 35°.<br /> <br /> ==='''Computational Domain CFD12'''===<br /> <br /> Symmetry is used to compute half the domain. No stilts included.<br /> <br /> Domain: [-3L;6L]x[0;0.9L]x[0;1.15L]<br /> <br /> Mesh : 1.3x106 cells<br /> <br /> Approximate value of y+ on solid surfaces : 1.5<br /> <br /> ==='''Boundary Conditions CFD12'''===<br /> <br /> Inlet: no details<br /> <br /> Solid boundaries: no-slip walls<br /> <br /> Symmetry plane: symmetry<br /> <br /> Other boundaries: farfield Riemann-invariant conditions<br /> <br /> ==='''Application of Physical Models CFD12'''===<br /> <br /> - SST model<br /> <br /> - Explicit Algebraic Stress Model with ω-equation<br /> <br /> ==='''Numerical Accuracy CFD12'''===<br /> <br /> Convection scheme : 1st order.<br /> <br /> ==='''CFD Results CFD12'''===<br /> <br /> The same quantities (except for triple correlations) as for experiment EXP2 are available in the Knowledge Base : results for the mean velocities U, V, W, Reynolds stresses [[Image:Image23.gif]] [[Image:Image24.gif]] [[Image:Image25.gif]] [[Image:Image26.gif]] [[Image:Image27.gif]] in some planes and profiles in the boundary layer above the slant part:<br /> <br /> <br /> <br /> '''SST model'''<br /> <br /> 25° slant angle:<br /> <br /> planes:<br /> &lt;span class=&quot;plainlinks&quot;&gt;[{{filepath:CFD12_SST_Ahmed_25_y=0.dat}} y=0]&lt;/span&gt;;<br /> &lt;span class=&quot;plainlinks&quot;&gt;[{{filepath:CFD12_SST_Ahmed_25_y=100.dat}} y=100]&lt;/span&gt;; <br /> &lt;span class=&quot;plainlinks&quot;&gt;[{{filepath:CFD12_SST_Ahmed_25_y=180.dat}} y=180]&lt;/span&gt;;<br /> <br /> &lt;span class=&quot;plainlinks&quot;&gt;[{{filepath:CFD12_SST_Ahmed_25_y=195.dat}} y=195]&lt;/span&gt;;<br /> &lt;span class=&quot;plainlinks&quot;&gt;[{{filepath:CFD12_SST_Ahmed_25_z=360.dat}} z=360]&lt;/span&gt;<br /> <br /> &lt;span class=&quot;plainlinks&quot;&gt;[{{filepath:CFD12_SST_Ahmed_25_x=-794.dat}} x=-794]&lt;/span&gt;;<br /> &lt;span class=&quot;plainlinks&quot;&gt;[{{filepath:CFD12_SST_Ahmed_25_x=-178.dat}} x=-178]&lt;/span&gt;;<br /> &lt;span class=&quot;plainlinks&quot;&gt;[{{filepath:CFD12_SST_Ahmed_25_x=-138.dat}} x=-138]&lt;/span&gt;;<br /> &lt;span class=&quot;plainlinks&quot;&gt;[{{filepath:CFD12_SST_Ahmed_25_x=-88.dat}} x=-88]&lt;/span&gt;;<br /> &lt;span class=&quot;plainlinks&quot;&gt;[{{filepath:CFD12_SST_Ahmed_25_x=-38.dat}} x=-38]&lt;/span&gt;;<br /> &lt;span class=&quot;plainlinks&quot;&gt;[{{filepath:CFD12_SST_Ahmed_25_x=0.dat}} x=0]&lt;/span&gt;;<br /> &lt;span class=&quot;plainlinks&quot;&gt;[{{filepath:CFD12_SST_Ahmed_25_x=80.dat}} x=80]&lt;/span&gt;;<br /> &lt;span class=&quot;plainlinks&quot;&gt;[{{filepath:CFD12_SST_Ahmed_25_x=200.dat}} x=200]&lt;/span&gt;;<br /> &lt;span class=&quot;plainlinks&quot;&gt;[{{filepath:CFD12_SST_Ahmed_25_x=500.dat}} x=500]&lt;/span&gt;<br /> <br /> profiles in the boundary layer:<br /> &lt;span class=&quot;plainlinks&quot;&gt;[{{filepath:CFD12_SST_Ahmed_25_BL_x=-243.dat}} x=-243]&lt;/span&gt;,<br /> &lt;span class=&quot;plainlinks&quot;&gt;[{{filepath:CFD12_SST_Ahmed_25_BL_x=-223.dat}} -223]&lt;/span&gt;,<br /> &lt;span class=&quot;plainlinks&quot;&gt;[{{filepath:CFD12_SST_Ahmed_25_BL_x=-203.dat}} -203]&lt;/span&gt;,<br /> &lt;span class=&quot;plainlinks&quot;&gt;[{{filepath:CFD12_SST_Ahmed_25_BL_x=-183.dat}} -183]&lt;/span&gt;,<br /> &lt;span class=&quot;plainlinks&quot;&gt;[{{filepath:CFD12_SST_Ahmed_25_BL_x=-163.dat}} -163]&lt;/span&gt;,<br /> &lt;span class=&quot;plainlinks&quot;&gt;[{{filepath:CFD12_SST_Ahmed_25_BL_x=-143.dat}} -143]&lt;/span&gt;,<br /> &lt;span class=&quot;plainlinks&quot;&gt;[{{filepath:CFD12_SST_Ahmed_25_BL_x=-123.dat}} -123]&lt;/span&gt;,<br /> &lt;span class=&quot;plainlinks&quot;&gt;[{{filepath:CFD12_SST_Ahmed_25_BL_x=-103.dat}} -103]&lt;/span&gt;,<br /> &lt;span class=&quot;plainlinks&quot;&gt;[{{filepath:CFD12_SST_Ahmed_25_BL_x=-83.dat}} -83]&lt;/span&gt;,<br /> &lt;span class=&quot;plainlinks&quot;&gt;[{{filepath:CFD12_SST_Ahmed_25_BL_x=-63.dat}} -63]&lt;/span&gt;,<br /> &lt;span class=&quot;plainlinks&quot;&gt;[{{filepath:CFD12_SST_Ahmed_25_BL_x=-43.dat}} -43]&lt;/span&gt;,<br /> &lt;span class=&quot;plainlinks&quot;&gt;[{{filepath:CFD12_SST_Ahmed_25_BL_x=-23.dat}} -23]&lt;/span&gt;,<br /> &lt;span class=&quot;plainlinks&quot;&gt;[{{filepath:CFD12_SST_Ahmed_25_BL_x=-3.dat}} -3]&lt;/span&gt;<br /> <br /> Pressure coefficients on the rear of the body:<br /> &lt;span class=&quot;plainlinks&quot;&gt;[{{filepath:CFD12_SST_Ahmed_25_Cp.dat}} Cp]&lt;/span&gt;<br /> <br /> <br /> 35° slant angle:<br /> <br /> planes:<br /> &lt;span class=&quot;plainlinks&quot;&gt;[{{filepath:CFD12_SST_Ahmed_35_y=0.dat}} y=0]&lt;/span&gt;;<br /> &lt;span class=&quot;plainlinks&quot;&gt;[{{filepath:CFD12_SST_Ahmed_35_y=100.dat}} y=100]&lt;/span&gt;; <br /> &lt;span class=&quot;plainlinks&quot;&gt;[{{filepath:CFD12_SST_Ahmed_35_y=180.dat}} y=180]&lt;/span&gt;;<br /> <br /> &lt;span class=&quot;plainlinks&quot;&gt;[{{filepath:CFD12_SST_Ahmed_35_y=195.dat}} y=195]&lt;/span&gt;;<br /> &lt;span class=&quot;plainlinks&quot;&gt;[{{filepath:CFD12_SST_Ahmed_35_z=360.dat}} z=360]&lt;/span&gt;<br /> <br /> &lt;span class=&quot;plainlinks&quot;&gt;[{{filepath:CFD12_SST_Ahmed_35_x=-794.dat}} x=-794]&lt;/span&gt;;<br /> &lt;span class=&quot;plainlinks&quot;&gt;[{{filepath:CFD12_SST_Ahmed_35_x=-178.dat}} x=-178]&lt;/span&gt;;<br /> &lt;span class=&quot;plainlinks&quot;&gt;[{{filepath:CFD12_SST_Ahmed_35_x=-138.dat}} x=-138]&lt;/span&gt;;<br /> &lt;span class=&quot;plainlinks&quot;&gt;[{{filepath:CFD12_SST_Ahmed_35_x=-88.dat}} x=-88]&lt;/span&gt;;<br /> &lt;span class=&quot;plainlinks&quot;&gt;[{{filepath:CFD12_SST_Ahmed_35_x=-38.dat}} x=-38]&lt;/span&gt;;<br /> &lt;span class=&quot;plainlinks&quot;&gt;[{{filepath:CFD12_SST_Ahmed_35_x=0.dat}} x=0]&lt;/span&gt;;<br /> &lt;span class=&quot;plainlinks&quot;&gt;[{{filepath:CFD12_SST_Ahmed_35_x=80.dat}} x=80]&lt;/span&gt;;<br /> &lt;span class=&quot;plainlinks&quot;&gt;[{{filepath:CFD12_SST_Ahmed_35_x=200.dat}} x=200]&lt;/span&gt;;<br /> &lt;span class=&quot;plainlinks&quot;&gt;[{{filepath:CFD12_SST_Ahmed_35_x=500.dat}} x=500]&lt;/span&gt;<br /> <br /> profiles in the boundary layer:<br /> &lt;span class=&quot;plainlinks&quot;&gt;[{{filepath:CFD12_SST_Ahmed_35_BL_x=-243.dat}} x=-243]&lt;/span&gt;,<br /> &lt;span class=&quot;plainlinks&quot;&gt;[{{filepath:CFD12_SST_Ahmed_35_BL_x=-223.dat}} -223]&lt;/span&gt;,<br /> &lt;span class=&quot;plainlinks&quot;&gt;[{{filepath:CFD12_SST_Ahmed_35_BL_x=-203.dat}} -203]&lt;/span&gt;,<br /> &lt;span class=&quot;plainlinks&quot;&gt;[{{filepath:CFD12_SST_Ahmed_35_BL_x=-183.dat}} -183]&lt;/span&gt;,<br /> &lt;span class=&quot;plainlinks&quot;&gt;[{{filepath:CFD12_SST_Ahmed_35_BL_x=-163.dat}} -163]&lt;/span&gt;,<br /> &lt;span class=&quot;plainlinks&quot;&gt;[{{filepath:CFD12_SST_Ahmed_35_BL_x=-143.dat}} -143]&lt;/span&gt;,<br /> &lt;span class=&quot;plainlinks&quot;&gt;[{{filepath:CFD12_SST_Ahmed_35_BL_x=-123.dat}} -123]&lt;/span&gt;,<br /> &lt;span class=&quot;plainlinks&quot;&gt;[{{filepath:CFD12_SST_Ahmed_35_BL_x=-103.dat}} -103]&lt;/span&gt;,<br /> &lt;span class=&quot;plainlinks&quot;&gt;[{{filepath:CFD12_SST_Ahmed_35_BL_x=-83.dat}} -83]&lt;/span&gt;,<br /> &lt;span class=&quot;plainlinks&quot;&gt;[{{filepath:CFD12_SST_Ahmed_35_BL_x=-63.dat}} -63]&lt;/span&gt;,<br /> &lt;span class=&quot;plainlinks&quot;&gt;[{{filepath:CFD12_SST_Ahmed_35_BL_x=-43.dat}} -43]&lt;/span&gt;,<br /> &lt;span class=&quot;plainlinks&quot;&gt;[{{filepath:CFD12_SST_Ahmed_35_BL_x=-23.dat}} -23]&lt;/span&gt;,<br /> &lt;span class=&quot;plainlinks&quot;&gt;[{{filepath:CFD12_SST_Ahmed_35_BL_x=-3.dat}} -3]&lt;/span&gt;<br /> <br /> Pressure coefficients on the rear of the body:<br /> &lt;span class=&quot;plainlinks&quot;&gt;[{{filepath:CFD12_SST_Ahmed_35_Cp.dat}} Cp]&lt;/span&gt;<br /> <br /> <br /> <br /> '''EASM model'''<br /> <br /> 25° slant angle:<br /> <br /> planes:<br /> &lt;span class=&quot;plainlinks&quot;&gt;[{{filepath:CFD12_EASM_Ahmed_25_y=0.dat}} y=0]&lt;/span&gt;;<br /> &lt;span class=&quot;plainlinks&quot;&gt;[{{filepath:CFD12_EASM_Ahmed_25_y=100.dat}} y=100]&lt;/span&gt;; <br /> &lt;span class=&quot;plainlinks&quot;&gt;[{{filepath:CFD12_EASM_Ahmed_25_y=180.dat}} y=180]&lt;/span&gt;;<br /> <br /> &lt;span class=&quot;plainlinks&quot;&gt;[{{filepath:CFD12_EASM_Ahmed_25_y=195.dat}} y=195]&lt;/span&gt;;<br /> &lt;span class=&quot;plainlinks&quot;&gt;[{{filepath:CFD12_EASM_Ahmed_25_z=360.dat}} z=360]&lt;/span&gt;<br /> <br /> &lt;span class=&quot;plainlinks&quot;&gt;[{{filepath:CFD12_EASM_Ahmed_25_x=-794.dat}} x=-794]&lt;/span&gt;;<br /> &lt;span class=&quot;plainlinks&quot;&gt;[{{filepath:CFD12_EASM_Ahmed_25_x=-178.dat}} x=-178]&lt;/span&gt;;<br /> &lt;span class=&quot;plainlinks&quot;&gt;[{{filepath:CFD12_EASM_Ahmed_25_x=-138.dat}} x=-138]&lt;/span&gt;;<br /> &lt;span class=&quot;plainlinks&quot;&gt;[{{filepath:CFD12_EASM_Ahmed_25_x=-88.dat}} x=-88]&lt;/span&gt;;<br /> &lt;span class=&quot;plainlinks&quot;&gt;[{{filepath:CFD12_EASM_Ahmed_25_x=-38.dat}} x=-38]&lt;/span&gt;;<br /> &lt;span class=&quot;plainlinks&quot;&gt;[{{filepath:CFD12_EASM_Ahmed_25_x=0.dat}} x=0]&lt;/span&gt;;<br /> &lt;span class=&quot;plainlinks&quot;&gt;[{{filepath:CFD12_EASM_Ahmed_25_x=80.dat}} x=80]&lt;/span&gt;;<br /> &lt;span class=&quot;plainlinks&quot;&gt;[{{filepath:CFD12_EASM_Ahmed_25_x=200.dat}} x=200]&lt;/span&gt;;<br /> &lt;span class=&quot;plainlinks&quot;&gt;[{{filepath:CFD12_EASM_Ahmed_25_x=500.dat}} x=500]&lt;/span&gt;<br /> <br /> profiles in the boundary layer:<br /> &lt;span class=&quot;plainlinks&quot;&gt;[{{filepath:CFD12_EASM_Ahmed_25_BL_x=-243.dat}} x=-243]&lt;/span&gt;,<br /> &lt;span class=&quot;plainlinks&quot;&gt;[{{filepath:CFD12_EASM_Ahmed_25_BL_x=-223.dat}} -223]&lt;/span&gt;,<br /> &lt;span class=&quot;plainlinks&quot;&gt;[{{filepath:CFD12_EASM_Ahmed_25_BL_x=-203.dat}} -203]&lt;/span&gt;,<br /> &lt;span class=&quot;plainlinks&quot;&gt;[{{filepath:CFD12_EASM_Ahmed_25_BL_x=-183.dat}} -183]&lt;/span&gt;,<br /> &lt;span class=&quot;plainlinks&quot;&gt;[{{filepath:CFD12_EASM_Ahmed_25_BL_x=-163.dat}} -163]&lt;/span&gt;,<br /> &lt;span class=&quot;plainlinks&quot;&gt;[{{filepath:CFD12_EASM_Ahmed_25_BL_x=-143.dat}} -143]&lt;/span&gt;,<br /> &lt;span class=&quot;plainlinks&quot;&gt;[{{filepath:CFD12_EASM_Ahmed_25_BL_x=-123.dat}} -123]&lt;/span&gt;,<br /> &lt;span class=&quot;plainlinks&quot;&gt;[{{filepath:CFD12_EASM_Ahmed_25_BL_x=-103.dat}} -103]&lt;/span&gt;,<br /> &lt;span class=&quot;plainlinks&quot;&gt;[{{filepath:CFD12_EASM_Ahmed_25_BL_x=-83.dat}} -83]&lt;/span&gt;,<br /> &lt;span class=&quot;plainlinks&quot;&gt;[{{filepath:CFD12_EASM_Ahmed_25_BL_x=-63.dat}} -63]&lt;/span&gt;,<br /> &lt;span class=&quot;plainlinks&quot;&gt;[{{filepath:CFD12_EASM_Ahmed_25_BL_x=-43.dat}} -43]&lt;/span&gt;,<br /> &lt;span class=&quot;plainlinks&quot;&gt;[{{filepath:CFD12_EASM_Ahmed_25_BL_x=-23.dat}} -23]&lt;/span&gt;,<br /> &lt;span class=&quot;plainlinks&quot;&gt;[{{filepath:CFD12_EASM_Ahmed_25_BL_x=-3.dat}} -3]&lt;/span&gt;<br /> <br /> Pressure coefficients on the rear of the body:<br /> &lt;span class=&quot;plainlinks&quot;&gt;[{{filepath:CFD12_EASM_Ahmed_25_Cp.dat}} Cp]&lt;/span&gt;<br /> <br /> <br /> 35° slant angle:<br /> <br /> planes:<br /> &lt;span class=&quot;plainlinks&quot;&gt;[{{filepath:CFD12_EASM_Ahmed_35_y=0.dat}} y=0]&lt;/span&gt;;<br /> &lt;span class=&quot;plainlinks&quot;&gt;[{{filepath:CFD12_EASM_Ahmed_35_y=100.dat}} y=100]&lt;/span&gt;; <br /> &lt;span class=&quot;plainlinks&quot;&gt;[{{filepath:CFD12_EASM_Ahmed_35_y=180.dat}} y=180]&lt;/span&gt;;<br /> <br /> &lt;span class=&quot;plainlinks&quot;&gt;[{{filepath:CFD12_EASM_Ahmed_35_y=195.dat}} y=195]&lt;/span&gt;;<br /> &lt;span class=&quot;plainlinks&quot;&gt;[{{filepath:CFD12_EASM_Ahmed_35_z=360.dat}} z=360]&lt;/span&gt;<br /> <br /> &lt;span class=&quot;plainlinks&quot;&gt;[{{filepath:CFD12_EASM_Ahmed_35_x=-794.dat}} x=-794]&lt;/span&gt;;<br /> &lt;span class=&quot;plainlinks&quot;&gt;[{{filepath:CFD12_EASM_Ahmed_35_x=-178.dat}} x=-178]&lt;/span&gt;;<br /> &lt;span class=&quot;plainlinks&quot;&gt;[{{filepath:CFD12_EASM_Ahmed_35_x=-138.dat}} x=-138]&lt;/span&gt;;<br /> &lt;span class=&quot;plainlinks&quot;&gt;[{{filepath:CFD12_EASM_Ahmed_35_x=-88.dat}} x=-88]&lt;/span&gt;;<br /> &lt;span class=&quot;plainlinks&quot;&gt;[{{filepath:CFD12_EASM_Ahmed_35_x=-38.dat}} x=-38]&lt;/span&gt;;<br /> &lt;span class=&quot;plainlinks&quot;&gt;[{{filepath:CFD12_EASM_Ahmed_35_x=0.dat}} x=0]&lt;/span&gt;;<br /> &lt;span class=&quot;plainlinks&quot;&gt;[{{filepath:CFD12_EASM_Ahmed_35_x=80.dat}} x=80]&lt;/span&gt;;<br /> &lt;span class=&quot;plainlinks&quot;&gt;[{{filepath:CFD12_EASM_Ahmed_35_x=200.dat}} x=200]&lt;/span&gt;;<br /> &lt;span class=&quot;plainlinks&quot;&gt;[{{filepath:CFD12_EASM_Ahmed_35_x=500.dat}} x=500]&lt;/span&gt;<br /> <br /> profiles in the boundary layer:<br /> &lt;span class=&quot;plainlinks&quot;&gt;[{{filepath:CFD12_EASM_Ahmed_35_BL_x=-243.dat}} x=-243]&lt;/span&gt;,<br /> &lt;span class=&quot;plainlinks&quot;&gt;[{{filepath:CFD12_EASM_Ahmed_35_BL_x=-223.dat}} -223]&lt;/span&gt;,<br /> &lt;span class=&quot;plainlinks&quot;&gt;[{{filepath:CFD12_EASM_Ahmed_35_BL_x=-203.dat}} -203]&lt;/span&gt;,<br /> &lt;span class=&quot;plainlinks&quot;&gt;[{{filepath:CFD12_EASM_Ahmed_35_BL_x=-183.dat}} -183]&lt;/span&gt;,<br /> &lt;span class=&quot;plainlinks&quot;&gt;[{{filepath:CFD12_EASM_Ahmed_35_BL_x=-163.dat}} -163]&lt;/span&gt;,<br /> &lt;span class=&quot;plainlinks&quot;&gt;[{{filepath:CFD12_EASM_Ahmed_35_BL_x=-143.dat}} -143]&lt;/span&gt;,<br /> &lt;span class=&quot;plainlinks&quot;&gt;[{{filepath:CFD12_EASM_Ahmed_35_BL_x=-123.dat}} -123]&lt;/span&gt;,<br /> &lt;span class=&quot;plainlinks&quot;&gt;[{{filepath:CFD12_EASM_Ahmed_35_BL_x=-103.dat}} -103]&lt;/span&gt;,<br /> &lt;span class=&quot;plainlinks&quot;&gt;[{{filepath:CFD12_EASM_Ahmed_35_BL_x=-83.dat}} -83]&lt;/span&gt;,<br /> &lt;span class=&quot;plainlinks&quot;&gt;[{{filepath:CFD12_EASM_Ahmed_35_BL_x=-63.dat}} -63]&lt;/span&gt;,<br /> &lt;span class=&quot;plainlinks&quot;&gt;[{{filepath:CFD12_EASM_Ahmed_35_BL_x=-43.dat}} -43]&lt;/span&gt;,<br /> &lt;span class=&quot;plainlinks&quot;&gt;[{{filepath:CFD12_EASM_Ahmed_35_BL_x=-23.dat}} -23]&lt;/span&gt;,<br /> &lt;span class=&quot;plainlinks&quot;&gt;[{{filepath:CFD12_EASM_Ahmed_35_BL_x=-3.dat}} -3]&lt;/span&gt;<br /> <br /> Pressure coefficients on the rear of the body:<br /> &lt;span class=&quot;plainlinks&quot;&gt;[{{filepath:CFD12_EASM_Ahmed_35_Cp.dat}} Cp]&lt;/span&gt;<br /> <br /> =='''References CFD12'''==<br /> <br /> C.L. Rumsey, Application of CFL3D to case 9.4 (Ahmed Body), in: R. Manceau, J.-P. Bonnet, editors, 10th ERCOFTAC (SIG-15)/IAHR/QNET-CFD Workshop on Refined Turbulence Modelling, Oct. 10-11, 2002, Laboratoire d’études aérodynamiques, UMR CNRS 6609, Université de Poitiers, France.<br /> <br /> <br /> =='''Simulation Case CFD13'''==<br /> <br /> ==='''Solution strategy CFD13'''===<br /> <br /> RANS modelling.<br /> <br /> In-house code STREAM, which is a finite volume solver which uses a structured, non-orthogonal curvilinear, multi block grid and a fully collocated arrangement. The SIMPLE pressure correction method and Rie &amp; Chow interpolation are used to prevent unrealistic pressure fluctuations. The convection terms are discretized using an upwind scheme or a TVD scheme based on the third-order QUICK scheme<br /> <br /> Reynolds number: 2.78x106 (see EXP2). Steady state computation.<br /> <br /> Slant angle: 25°.<br /> <br /> ==='''Computational Domain CFD13'''===<br /> <br /> Symmetry is used to compute half the domain. No stilts included.<br /> <br /> Domain: [-3L;6L]x[0;0.9L]x[0;1.15L]<br /> <br /> Mesh : 1.3x106 cells<br /> <br /> Approximate value of y+ on solid surfaces : 1<br /> <br /> ==='''Boundary Conditions CFD13'''===<br /> <br /> Inlet: no details<br /> <br /> Solid boundaries: no-slip walls<br /> <br /> Other boundaries: symmetry<br /> <br /> ===''''Application of Physical Models CFD13'''===<br /> <br /> All are low-Reynolds number models<br /> <br /> - Linear k-ε model (Launder-Sharma)<br /> <br /> - Linear k-ω model (Wilcox)<br /> <br /> - Cubic k-ε model (Apsley, Leschziner)<br /> <br /> - Quadratic k-ω model (Abe, Jang, Leschziner)<br /> <br /> - Quadratic k-ε model (Abe, Jang, Leschziner)<br /> <br /> - SSG + Chen (Abe, Jang, Leschziner)<br /> <br /> ==='''Numerical Accuracy CFD13'''===<br /> <br /> No details<br /> <br /> ==='''CFD Results CFD13'''===<br /> <br /> Cp contours on the slant part, velocity profiles in the boundary layer over the slant part, vectors plots in 13 planes (see EXP2).<br /> <br /> =='''References CFD13'''==<br /> '''Y.J. Jang, M. Leschziner, Contribution of Imperial College to Test Case 9.4: Flow around a simplified car body, In: R. Manceau, J.-P. Bonnet, editors, '''''10th ERCOFTAC (SIG-15)/IAHR/QNET-CFD Workshop on Refined Turbulence Modelling, Oct. 10-11, 2002, Laboratoire d’études aérodynamiques, UMR CNRS 6609, Université de Poitiers, France.'''''<br /> <br /> <br /> =='''Simulation Case CFD14'''==<br /> <br /> ==='''Solution strategy CFD14'''===<br /> <br /> RANS modelling.<br /> <br /> In-house code ISIS, based on unstructured finite volume discretization.<br /> <br /> Reynolds number: 2.78x106 (see EXP2). Steady state computation.<br /> <br /> Slant angle: 25° and 35°.<br /> <br /> ==='''Computational Domain CFD14'''===<br /> <br /> Symmetry is used to compute half the domain.<br /> <br /> Domain: [-4L;5L]x[0;0.9L]x[0;1.35L]<br /> <br /> Mesh : 3.8x106 cells<br /> <br /> Approximate value of y+ on solid surfaces: 0.5<br /> <br /> ==='''Boundary Conditions CFD14'''===<br /> <br /> Solid boundaries: no slip wall<br /> <br /> Symmetry plane: symmetry<br /> <br /> Other boundaries: no details<br /> <br /> ==='''Application of Physical Models CFD14'''===<br /> <br /> SST model<br /> <br /> ==='''Numerical Accuracy CFD14'''===<br /> <br /> No details<br /> <br /> ==='''CFD Results CFD14'''===<br /> <br /> Velocity profiles in the boundary layer over the slant part, streamlines, turbulent energy contours.<br /> <br /> =='''References CFD14'''==<br /> <br /> E. Guilmineau, Numerical simulation of flow around a simplified car body, Proc. ASME JSME Joint Fluids Engineering Conference, July 6-10, 2003, Honolulu, Hawaii, USA<br /> <br /> <br /> =='''Simulation Case CFD15'''==<br /> <br /> ==='''Solution strategy CFD15'''===<br /> <br /> RANS modelling.<br /> <br /> Commercial StarCD code, based on unstructured finite volume discretization.<br /> <br /> Reynolds number: 2.78x106 (see EXP2). Steady state computation.<br /> <br /> Slant angle: 25°.<br /> <br /> ==='''Computational Domain CFD15'''===<br /> <br /> Symmetry is used to compute half the domain. No stilts included. The ground plate starts 2L upstream of the body in order to reproduce the experimental boundary layer.<br /> <br /> Domain: [-5.75L;5.75L]x[0;L]x[0;1.35L]<br /> <br /> Mesh : 1.6x106 cells<br /> <br /> Approximate value of y+ on solid surfaces : &lt; 3<br /> <br /> ==='''Boundary Conditions CFD15'''===<br /> <br /> Inlet: turbulence level 0.1%, nt/n=10.<br /> <br /> Outlet: convective outlet.<br /> <br /> Solid boundaries: no-slip walls<br /> <br /> Symmetry plane: symmetry<br /> <br /> Other boundaries: symmetry<br /> <br /> ==='''Application of Physical Models CFD15'''===<br /> <br /> Rescaled V2F model (Manceau, Carlson, Gatski)<br /> <br /> ==='''Numerical Accuracy CFD15'''===<br /> <br /> No details.<br /> <br /> ==='''CFD Results CFD15'''===<br /> <br /> Vector plots.<br /> <br /> =='''References CFD15'''==<br /> <br /> R. Manceau, Computation of the flow around a simplified car using the rescaled v2f model, ''Proc. ASME JSME Joint Fluids Engineering Conference, July 6-10, 2003, Honolulu, Hawaii, USA''<br /> <br /> <br /> {| align=&quot;center&quot; width=&quot;700&quot; border=&quot;1&quot;<br /> |+ align=&quot;bottom&quot; | Table CFD-A Summary Description of CFD1 - CFD15 Test Cases<br /> ! NAME<br /> ! Re x 10&lt;sup&gt;-6&lt;/sup&gt;<br /> ! width=&quot;90&quot; | Slant angle (degrees)<br /> ! colspan=&quot;2&quot; | [[DOAPs#SPs:_Simulated_Parameters|SPs]]<br /> |-<br /> |<br /> |<br /> |<br /> ! width=&quot;80&quot; | Detailed Data<br /> ! [[DOAPs#DOAPs:_Design_or_Assessment_Parameters|DOAP]]<br /> |-<br /> ! align=&quot;left&quot; | CFD1<br /> | align=&quot;center&quot; | 4.29<br /> | align=&quot;center&quot; | 0, 10, 12, 20, 25, 30, 40, 50<br /> | align=&quot;center&quot; | Pressure&amp;nbsp;Tomographies<br /> | align=&quot;center&quot; | C&lt;sub&gt;d&lt;/sub&gt;, Streamlines, Friction&amp;nbsp;Lines<br /> |-<br /> ! align=&quot;left&quot; | CFD2<br /> | align=&quot;center&quot; | 4.29<br /> | align=&quot;center&quot; | 30<br /> | align=&quot;center&quot; | Effective&amp;nbsp;Viscosity<br /> | align=&quot;center&quot; | C&lt;sub&gt;D&lt;/sub&gt;, Velocities<br /> |-<br /> ! align=&quot;left&quot; | CFD3<br /> | align=&quot;center&quot; | 4.29<br /> | align=&quot;center&quot; | 28<br /> | align=&quot;center&quot; | Pressure&amp;nbsp;Coefficient, Q-criterion&amp;nbsp;Contours<br /> | align=&quot;center&quot; | C&lt;sub&gt;d&lt;/sub&gt;, Velocities, Vorticity&amp;nbsp;Contours<br /> |-<br /> ! align=&quot;left&quot; | CFD4<br /> | align=&quot;center&quot; | 2.78<br /> | align=&quot;center&quot; | 25, 35<br /> | align=&quot;center&quot; | C&lt;sub&gt;P&lt;/sub&gt;<br /> | align=&quot;center&quot; | Velocity&amp;nbsp;Profiles<br /> |-<br /> ! align=&quot;left&quot; | CFD5<br /> | align=&quot;center&quot; | 2.78<br /> | align=&quot;center&quot; | 25, 35<br /> | align=&quot;center&quot; | C&lt;sub&gt;P&lt;/sub&gt;, Turbulent&amp;nbsp;Energy&amp;nbsp;Contours<br /> | align=&quot;center&quot; | Velocity&amp;nbsp;Profiles, Vector&amp;nbsp;Plots, Streamlines<br /> |-<br /> ! align=&quot;left&quot; | CFD6<br /> | align=&quot;center&quot; | 2.78<br /> | align=&quot;center&quot; | 25<br /> | align=&quot;center&quot; | C&lt;sub&gt;P&lt;/sub&gt;<br /> | align=&quot;center&quot; | Velocity&amp;nbsp;Profiles<br /> |-<br /> ! align=&quot;left&quot; | CFD7<br /> | align=&quot;center&quot; | 2.78<br /> | align=&quot;center&quot; | 35<br /> | align=&quot;center&quot; | C&lt;sub&gt;P&lt;/sub&gt;<br /> | align=&quot;center&quot; | Velocity&amp;nbsp;Profiles, Vector&amp;nbsp;Plots<br /> |-<br /> ! align=&quot;left&quot; | CFD8<br /> | align=&quot;center&quot; | 2.78<br /> | align=&quot;center&quot; | 25, 35<br /> | align=&quot;center&quot; | C&lt;sub&gt;P&lt;/sub&gt;<br /> | align=&quot;center&quot; | Velocity&amp;nbsp;Profiles, Vector&amp;nbsp;Plots<br /> |-<br /> ! align=&quot;left&quot; | CFD9<br /> | align=&quot;center&quot; | 2.78<br /> | align=&quot;center&quot; | 25, 35<br /> | align=&quot;center&quot; | C&lt;sub&gt;P&lt;/sub&gt;<br /> | align=&quot;center&quot; | Velocity&amp;nbsp;Profiles, Vector&amp;nbsp;Plots<br /> |-<br /> ! align=&quot;left&quot; | CFD10<br /> | align=&quot;center&quot; | 2.78<br /> | align=&quot;center&quot; | 25<br /> | align=&quot;center&quot; | C&lt;sub&gt;P&lt;/sub&gt;<br /> | align=&quot;center&quot; | Velocity&amp;nbsp;Profiles, Vector&amp;nbsp;Plots<br /> |-<br /> ! align=&quot;left&quot; | CFD11<br /> | align=&quot;center&quot; | 2.78<br /> | align=&quot;center&quot; | 35<br /> | align=&quot;center&quot; | C&lt;sub&gt;P&lt;/sub&gt;<br /> | align=&quot;center&quot; | C&lt;sub&gt;d&lt;/sub&gt;, Velocity&amp;nbsp;Profiles, Vector&amp;nbsp;Plots<br /> |-<br /> ! align=&quot;left&quot; | CFD12<br /> | align=&quot;center&quot; | 2.78<br /> | align=&quot;center&quot; | 25, 35<br /> | align=&quot;center&quot; | C&lt;sub&gt;P&lt;/sub&gt;<br /> | align=&quot;center&quot; | Velocity&amp;nbsp;Profiles, Vector&amp;nbsp;Plots<br /> |-<br /> ! align=&quot;left&quot; | CFD13<br /> | align=&quot;center&quot; | 2.78<br /> | align=&quot;center&quot; | 25<br /> | align=&quot;center&quot; | C&lt;sub&gt;P&lt;/sub&gt;<br /> | align=&quot;center&quot; | Velocity&amp;nbsp;Profiles, Vector&amp;nbsp;Plots<br /> |-<br /> ! align=&quot;left&quot; | CFD14<br /> | align=&quot;center&quot; | 2.78<br /> | align=&quot;center&quot; | 25, 35<br /> | align=&quot;center&quot; | Turbulent&amp;nbsp;Energy&amp;nbsp;Contours<br /> | align=&quot;center&quot; | Velocity&amp;nbsp;Profiles, Streamlines<br /> |-<br /> ! align=&quot;left&quot; | CFD15<br /> | align=&quot;center&quot; | 2.78<br /> | align=&quot;center&quot; | 25<br /> |<br /> | align=&quot;center&quot; | Vector&amp;nbsp;Plots<br /> |}<br /> <br /> =='''Simulation Case CFD16 (added in 2024 by F.R. Menter)'''==<br /> <br /> ==='''Solution Strategy CFD16'''===<br /> <br /> Large Eddy Simulation – Several simulations using different wall treatments and different meshes. <br /> <br /> Commercial Fluent and Fluent-GPU codes<br /> <br /> Reynolds number 2.78e6 (EXP2) (also simulations for lower Re=0.72e6)<br /> <br /> Slant angle 25°<br /> <br /> ==='''Computational Domain CFD16'''===<br /> <br /> All geometry included.<br /> <br /> Domain [m] [-3,6] x [-3,3] x [0, 3.5]<br /> <br /> Meshes from 7e6 to 560e6. (given in reference)<br /> <br /> Y+ values varying for different meshes (wall-resolved to wall function meshes)<br /> <br /> ==='''Boundary Conditions CFD16'''===<br /> <br /> Inlet – Velocity constant<br /> <br /> Bottom wind tunnel wall: non-slip<br /> <br /> Other wind tunnel walls: Slip walls<br /> <br /> Outlet: Pressure outlet<br /> <br /> ==='''Application of Physical Models CFD16'''===<br /> <br /> (described in Fluent Manual A.F.U. R-22.1, 2022)<br /> <br /> WALE model<br /> <br /> Wall-Resolved LES<br /> <br /> Wall-Function LES<br /> <br /> ==='''Numerical Accuracy CFD16'''===<br /> <br /> 2nd order code<br /> <br /> Wide range of meshes (given in reference)<br /> <br /> ==='''CFD Results CFD16'''===<br /> <br /> Wall shear stress on the roof-center plane, velocity and streamwise fluctuation profiles on the slant, wall streamlines on the slant, turbulent structures around the car body.<br /> <br /> =='''References CFD16'''==<br /> <br /> Menter, F.R., Hüppe, A., Flad, D. et al. Large Eddy Simulations for the Ahmed Car at 25° Slant Angle at Different Reynolds Numbers. Flow Turbulence Combust 112, 321–343 (2024).<br /> <br /> <br /> <br /> <br /> © copyright ERCOFTAC 2004<br /> <br /> ----<br /> <br /> <br /> ''Contributors: Remi Manceau; Jean-Paul Bonnet - Université de Poitiers. Update (2024) F.R.Menter, ANSYS Germany'', <br /> <br /> Site Design and Implementation:[[Atkins]] and [[UniS]]<br /> <br /> {{AC|front=AC 1-05|description=Description_AC1-05|testdata=Test Data_AC1-05|cfdsimulations=CFD Simulations_AC1-05|evaluation=Evaluation_AC1-05|qualityreview=Quality Review_AC1-05|bestpractice=Best Practice Advice_AC1-05|relatedUFRs=Related UFRs_AC1-05}}</div> Mike https://kbwiki.ercoftac.org/w/index.php?title=Description_AC1-05&diff=45195 Description AC1-05 2024-02-09T09:37:25Z <p>Mike: </p> <hr /> <div>{{AC|front=AC 1-05|description=Description_AC1-05|testdata=Test Data_AC1-05|cfdsimulations=CFD Simulations_AC1-05|evaluation=Evaluation_AC1-05|qualityreview=Quality Review_AC1-05|bestpractice=Best Practice Advice_AC1-05|relatedUFRs=Related UFRs_AC1-05}}<br /> <br /> ='''Ahmed body'''=<br /> <br /> '''Application Challenge 1-05''' © copyright ERCOFTAC 2004<br /> <br /> <br /> <br /> =='''Introduction'''==<br /> <br /> A basic ground vehicle type of bluff body is investigated. The body consists of three parts : a fore-body, a mid section and a rear end.<br /> <br /> Two experiments are available:<br /> <br /> The first one (Exp1) was performed at DLR-Göttingen in a wind tunnel at Reynolds number 4.29 million (60 m/s), based on the model length. The model is mounted on a ground plate, in order to reproduce the ground effect. The angle of the rear end slope is adjustable, between 0 and 40° with a 5° step. More details are available for angles of 5°, 12.5° and 30°. Pressure is measured by about 210 pressure probes on the fore-body, 83 in the mid section and 450 on rear ends. Friction lines <br /> visualizations are also available. Moreover, detailed wake surveys are performed with 10 hole probes and drag measurements are provided.<br /> <br /> <br /> <br /> The second, more recent experiment (Exp2) was provided by Erlangen LSTM within the MOVA “Models for Vehicle Aerodynamics” European project (TU Delft, Univ. of Manchester (UMIST), LSTM, Electricité de France, AVL List, PSA Peugeot-Citroën). The same model is used as in the previous study, but the Reynolds number is reduced to 2.78 million (40m/s), and the study is focused on slant angles close to the drag crisis, 25° and 35°. Two-component hot wire measurements were performed in the boundary layer above the slant part and LDA measurements in 13 different planes. Mean values and turbulence statistics (second and third moments) are provided. Pressure measurements were performed on the rear part of the model (435 pressure probes). Oil/soot friction lines visualizations are also provided.<br /> <br /> The Ahmed body was one of the test cases of the 9th and 10th ERCOFTAC-IAHR Workshop on Refined Turbulence Modeling held in Darmstad, Germany (2001) and Poitiers, France (2002) respectively. These workshops were organized under the auspices of the Special Interest Group 15 on Turbulence Modeling of ERCOFTAC. The proceedings of the 10th ERCOFTAC-IAHR Workshop can be found at:<br /> <br /> [http://www.ercoftac.nl/workshop10/index.html http://www.ercoftac.nl/workshop10/index.html]<br /> <br /> and this test case at:<br /> <br /> [http://www.ercoftac.nl/workshop10/case9.4/case9.4.html http://www.ercoftac.nl/workshop10/case9.4/case9.4.html]<br /> <br /> CFD results were obtained by 15 different teams, ranging from simple RANS models (standard k-epsilon model with wall functions) to more elaborate RANS models and even LES.<br /> <br /> After the ERCOFTAC workshops in the early 2000’s, CFD simulations were mainly carried out with LES and hybrid RANS-LES methods. An update on these simulations was added in 2024 to this document by F.R. Menter including LES results for the 25° slant angle case from Menter et al (2024) - Reference see Abstract.<br /> <br /> =='''Relevance to Industrial Sector'''==<br /> <br /> The basic shape of the so-called « Ahmed body » contains important features of real road vehicles : a main body, followed by a fully separated region. Prediction of separated flows is one of the more difficult task of CFD. The parametric variation of the angle of the rear part allows the study of various configuration relevant to real car characteristics, from massively separated, “simple” wakes, to very complex, 3D wake structures. The reproduction of this complex, 3D wake is very challenging for CFD, as well as the transition from one behaviour to another. The data base contains also drag results that are essential to predict for practical purposes, and are closely related to the structure of the wake.<br /> <br /> The second set of experiments provides very detailed results, including turbulent quantities that are useful for a detailed analysis of turbulence models.<br /> <br /> <br /> =='''Design or Assessment Parameters'''==<br /> <br /> The first [[DOAP]] is the drag coefficient, and in particular its variations with the slant angle.<br /> <br /> A second [[DOAP]] is the topology of the flow, which is crucial for the correct reproduction of the drag coefficient. Comparisons between computations and experiments in the provided planes and in the boundary layer will be useful, as well as friction lines visualizations on the slant part and the vertical base.<br /> <br /> <br /> =='''Flow Domain Geometry'''==<br /> <br /> <br /> {|align=&quot;center&quot;<br /> |[[Image:Image22.gif]]<br /> |-<br /> |''Figure 1:'' Geometry of the Ahmed body <br /> |}<br /> <br /> <br /> <br /> The model is described on Figure 1. The geometry of the fore-body is available in<br /> &lt;span class=&quot;plainlinks&quot;&gt;[{{filepath:Ahmed_Front_Geo.dat}} Ahmed_Front_Geo.dat]&lt;/span&gt;.<br /> <br /> X, Y and Z are the streamwise, spanwise and ground-normal directions, respectively. The origin of the axes is the point at the intersection between the vertical base (X=0), the symmetry plane (Y=0) and the ground plate (Z=0).<br /> <br /> Overall length: 1.044 m. Width 0.389 m, Height 0.288 m.<br /> <br /> The forebody is 0.182 m long, the center of the curvature being placed 100 mm from the front and upper/lower/lateral surfaces. The central (constant section area) is 0.640 m long.<br /> <br /> All rear ends have the same slant part length Ls= 222mm. The edges are sharp.<br /> <br /> The model is placed in a 3/4-open test section (only the floor is present). No indication on the homogeneity of the flow is given.<br /> <br /> Special attention should be given on the presence of a ground plate between the tunnel floor and the body. This plate is used for preventing wind tunnel boundary layer parasitic effects on the model. The model lies 50 mm above it and is placed on stilts of 30 mm diameter.<br /> <br /> =='''Flow Physics and Fluid Dynamics Data'''==<br /> <br /> The flow has no special characteristics. Air at ambiant conditions is used. The model is supposed to be smooth.<br /> <br /> © copyright ERCOFTAC 2004<br /> <br /> ----<br /> <br /> <br /> ''Contributors: Remi Manceau; Jean-Paul Bonnet - Université de Poitiers. Update (2024) F.R.Menter, ANSYS Germany'', <br /> <br /> <br /> {{AC|front=AC 1-05|description=Description_AC1-05|testdata=Test Data_AC1-05|cfdsimulations=CFD Simulations_AC1-05|evaluation=Evaluation_AC1-05|qualityreview=Quality Review_AC1-05|bestpractice=Best Practice Advice_AC1-05|relatedUFRs=Related UFRs_AC1-05}}</div> Mike https://kbwiki.ercoftac.org/w/index.php?title=Description_AC1-05&diff=45194 Description AC1-05 2024-02-09T09:36:57Z <p>Mike: </p> <hr /> <div>{{AC|front=AC 1-05|description=Description_AC1-05|testdata=Test Data_AC1-05|cfdsimulations=CFD Simulations_AC1-05|evaluation=Evaluation_AC1-05|qualityreview=Quality Review_AC1-05|bestpractice=Best Practice Advice_AC1-05|relatedUFRs=Related UFRs_AC1-05}}<br /> <br /> ='''Ahmed body'''=<br /> <br /> '''Application Challenge 1-05''' © copyright ERCOFTAC 2004<br /> <br /> <br /> <br /> =='''Introduction'''==<br /> <br /> A basic ground vehicle type of bluff body is investigated. The body consists of three parts : a fore-body, a mid section and a rear end.<br /> <br /> Two experiments are available:<br /> <br /> The first one (Exp1) was performed at DLR-Göttingen in a wind tunnel at Reynolds number 4.29 million (60 m/s), based on the model length. The model is mounted on a ground plate, in order to reproduce the ground effect. The angle of the rear end slope is adjustable, between 0 and 40° with a 5° step. More details are available for angles of 5°, 12.5° and 30°. Pressure is measured by about 210 pressure probes on the fore-body, 83 in the mid section and 450 on rear ends. Friction lines <br /> visualizations are also available. Moreover, detailed wake surveys are performed with 10 hole probes and drag measurements are provided.<br /> <br /> <br /> <br /> The second, more recent experiment (Exp2) was provided by Erlangen LSTM within the MOVA “Models for Vehicle Aerodynamics” European project (TU Delft, Univ. of Manchester (UMIST), LSTM, Electricité de France, AVL List, PSA Peugeot-Citroën). The same model is used as in the previous study, but the Reynolds number is reduced to 2.78 million (40m/s), and the study is focused on slant angles close to the drag crisis, 25° and 35°. Two-component hot wire measurements were performed in the boundary layer above the slant part and LDA measurements in 13 different planes. Mean values and turbulence statistics (second and third moments) are provided. Pressure measurements were performed on the rear part of the model (435 pressure probes). Oil/soot friction lines visualizations are also provided.<br /> <br /> The Ahmed body was one of the test cases of the 9th and 10th ERCOFTAC-IAHR Workshop on Refined Turbulence Modeling held in Darmstad, Germany (2001) and Poitiers, France (2002) respectively. These workshops were organized under the auspices of the Special Interest Group 15 on Turbulence Modeling of ERCOFTAC. The proceedings of the 10th ERCOFTAC-IAHR Workshop can be found at:<br /> <br /> [http://www.ercoftac.nl/workshop10/index.html http://www.ercoftac.nl/workshop10/index.html]<br /> <br /> and this test case at:<br /> <br /> [http://www.ercoftac.nl/workshop10/case9.4/case9.4.html http://www.ercoftac.nl/workshop10/case9.4/case9.4.html]<br /> <br /> CFD results were obtained by 15 different teams, ranging from simple RANS models (standard k-epsilon model with wall functions) to more elaborate RANS models and even LES.<br /> <br /> After the ERCOFTAC workshops in the early 2000’s, CFD simulations were mainly carried out with LES and hybrid RANS-LES methods. An update on these simulations was added in 2024 to this document by F.R. Menter including LES results for the 25° slant angle case from Menter et al (2024) - Reference see Abstract.<br /> <br /> =='''Relevance to Industrial Sector'''==<br /> <br /> The basic shape of the so-called « Ahmed body » contains important features of real road vehicles : a main body, followed by a fully separated region. Prediction of separated flows is one of the more difficult task of CFD. The parametric variation of the angle of the rear part allows the study of various configuration relevant to real car characteristics, from massively separated, “simple” wakes, to very complex, 3D wake structures. The reproduction of this complex, 3D wake is very challenging for CFD, as well as the transition from one behaviour to another. The data base contains also drag results that are essential to predict for practical purposes, and are closely related to the structure of the wake.<br /> <br /> The second set of experiments provides very detailed results, including turbulent quantities that are useful for a detailed analysis of turbulence models.<br /> <br /> <br /> =='''Design or Assessment Parameters'''==<br /> <br /> The first [[DOAP]] is the drag coefficient, and in particular its variations with the slant angle.<br /> <br /> A second [[DOAP]] is the topology of the flow, which is crucial for the correct reproduction of the drag coefficient. Comparisons between computations and experiments in the provided planes and in the boundary layer will be useful, as well as friction lines visualizations on the slant part and the vertical base.<br /> <br /> <br /> =='''Flow Domain Geometry'''==<br /> <br /> <br /> {|align=&quot;center&quot;<br /> |[[Image:Image22.gif]]<br /> |-<br /> |''Figure 1:'' Geometry of the Ahmed body <br /> |}<br /> <br /> <br /> <br /> The model is described on Figure 1. The geometry of the fore-body is available in<br /> &lt;span class=&quot;plainlinks&quot;&gt;[{{filepath:Ahmed_Front_Geo.dat}} Ahmed_Front_Geo.dat]&lt;/span&gt;.<br /> <br /> X, Y and Z are the streamwise, spanwise and ground-normal directions, respectively. The origin of the axes is the point at the intersection between the vertical base (X=0), the symmetry plane (Y=0) and the ground plate (Z=0).<br /> <br /> Overall length: 1.044 m. Width 0.389 m, Height 0.288 m.<br /> <br /> The forebody is 0.182 m long, the center of the curvature being placed 100 mm from the front and upper/lower/lateral surfaces. The central (constant section area) is 0.640 m long.<br /> <br /> All rear ends have the same slant part length Ls= 222mm. The edges are sharp.<br /> <br /> The model is placed in a 3/4-open test section (only the floor is present). No indication on the homogeneity of the flow is given.<br /> <br /> Special attention should be given on the presence of a ground plate between the tunnel floor and the body. This plate is used for preventing wind tunnel boundary layer parasitic effects on the model. The model lies 50 mm above it and is placed on stilts of 30 mm diameter.<br /> <br /> =='''Flow Physics and Fluid Dynamics Data'''==<br /> <br /> The flow has no special characteristics. Air at ambiant conditions is used. The model is supposed to be smooth.<br /> <br /> © copyright ERCOFTAC 2004<br /> <br /> ----<br /> <br /> <br /> ''Contributors: Remi Manceau; Jean-Paul Bonnet - Université de Poitiers. Update (2024) F.R.Menter, ANSYS Germany'', <br /> <br /> Site Design and Implementation: [[Atkins]] and [[UniS]]<br /> <br /> {{AC|front=AC 1-05|description=Description_AC1-05|testdata=Test Data_AC1-05|cfdsimulations=CFD Simulations_AC1-05|evaluation=Evaluation_AC1-05|qualityreview=Quality Review_AC1-05|bestpractice=Best Practice Advice_AC1-05|relatedUFRs=Related UFRs_AC1-05}}</div> Mike https://kbwiki.ercoftac.org/w/index.php?title=Description_AC1-05&diff=45193 Description AC1-05 2024-02-09T09:35:41Z <p>Mike: </p> <hr /> <div>{{AC|front=AC 1-05|description=Description_AC1-05|testdata=Test Data_AC1-05|cfdsimulations=CFD Simulations_AC1-05|evaluation=Evaluation_AC1-05|qualityreview=Quality Review_AC1-05|bestpractice=Best Practice Advice_AC1-05|relatedUFRs=Related UFRs_AC1-05}}<br /> <br /> ='''Ahmed body'''=<br /> <br /> '''Application Challenge 1-05''' © copyright ERCOFTAC 2004<br /> <br /> <br /> <br /> =='''Introduction'''==<br /> <br /> A basic ground vehicle type of bluff body is investigated. The body consists of three parts : a fore-body, a mid section and a rear end.<br /> <br /> Two experiments are available:<br /> <br /> The first one (Exp1) was performed at DLR-Göttingen in a wind tunnel at Reynolds number 4.29 million (60 m/s), based on the model length. The model is mounted on a ground plate, in order to reproduce the ground effect. The angle of the rear end slope is adjustable, between 0 and 40° with a 5° step. More details are available for angles of 5°, 12.5° and 30°. Pressure is measured by about 210 pressure probes on the fore-body, 83 in the mid section and 450 on rear ends. Friction lines <br /> visualizations are also available. Moreover, detailed wake surveys are performed with 10 hole probes and drag measurements are provided.<br /> <br /> <br /> <br /> The second, more recent experiment (Exp2) was provided by Erlangen LSTM within the MOVA “Models for Vehicle Aerodynamics” European project (TU Delft, Univ. of Manchester (UMIST), LSTM, Electricité de France, AVL List, PSA Peugeot-Citroën). The same model is used as in the previous study, but the Reynolds number is reduced to 2.78 million (40m/s), and the study is focused on slant angles close to the drag crisis, 25° and 35°. Two-component hot wire measurements were performed in the boundary layer above the slant part and LDA measurements in 13 different planes. Mean values and turbulence statistics (second and third moments) are provided. Pressure measurements were performed on the rear part of the model (435 pressure probes). Oil/soot friction lines visualizations are also provided.<br /> <br /> The Ahmed body was one of the test cases of the 9th and 10th ERCOFTAC-IAHR Workshop on Refined Turbulence Modeling held in Darmstad, Germany (2001) and Poitiers, France (2002) respectively. These workshops were organized under the auspices of the Special Interest Group 15 on Turbulence Modeling of ERCOFTAC. The proceedings of the 10th ERCOFTAC-IAHR Workshop can be found at:<br /> <br /> [http://www.ercoftac.nl/workshop10/index.html http://www.ercoftac.nl/workshop10/index.html]<br /> <br /> and this test case at:<br /> <br /> [http://www.ercoftac.nl/workshop10/case9.4/case9.4.html http://www.ercoftac.nl/workshop10/case9.4/case9.4.html]<br /> <br /> CFD results were obtained by 15 different teams, ranging from simple RANS models (standard k-epsilon model with wall functions) to more elaborate RANS models and even LES.<br /> <br /> After the ERCOFTAC workshops in the early 2000’s, CFD simulations were mainly carried out with LES and hybrid RANS-LES methods. An update on these simulations was added in 2024 to this document by F.R. Menter including LES results for the 25° slant angle case from Menter et al (2024) - Reference see Abstract.<br /> <br /> =='''Relevance to Industrial Sector'''==<br /> <br /> The basic shape of the so-called « Ahmed body » contains important features of real road vehicles : a main body, followed by a fully separated region. Prediction of separated flows is one of the more difficult task of CFD. The parametric variation of the angle of the rear part allows the study of various configuration relevant to real car characteristics, from massively separated, “simple” wakes, to very complex, 3D wake structures. The reproduction of this complex, 3D wake is very challenging for CFD, as well as the transition from one behaviour to another. The data base contains also drag results that are essential to predict for practical purposes, and are closely related to the structure of the wake.<br /> <br /> The second set of experiments provides very detailed results, including turbulent quantities that are useful for a detailed analysis of turbulence models.<br /> <br /> <br /> =='''Design or Assessment Parameters'''==<br /> <br /> The first [[DOAP]] is the drag coefficient, and in particular its variations with the slant angle.<br /> <br /> A second [[DOAP]] is the topology of the flow, which is crucial for the correct reproduction of the drag coefficient. Comparisons between computations and experiments in the provided planes and in the boundary layer will be useful, as well as friction lines visualizations on the slant part and the vertical base.<br /> <br /> <br /> =='''Flow Domain Geometry'''==<br /> <br /> <br /> {|align=&quot;center&quot;<br /> |[[Image:Image22.gif]]<br /> |-<br /> |''Figure 1:'' Geometry of the Ahmed body <br /> |}<br /> <br /> <br /> <br /> The model is described on Figure 1. The geometry of the fore-body is available in<br /> &lt;span class=&quot;plainlinks&quot;&gt;[{{filepath:Ahmed_Front_Geo.dat}} Ahmed_Front_Geo.dat]&lt;/span&gt;.<br /> <br /> X, Y and Z are the streamwise, spanwise and ground-normal directions, respectively. The origin of the axes is the point at the intersection between the vertical base (X=0), the symmetry plane (Y=0) and the ground plate (Z=0).<br /> <br /> Overall length: 1.044 m. Width 0.389 m, Height 0.288 m.<br /> <br /> The forebody is 0.182 m long, the center of the curvature being placed 100 mm from the front and upper/lower/lateral surfaces. The central (constant section area) is 0.640 m long.<br /> <br /> All rear ends have the same slant part length Ls= 222mm. The edges are sharp.<br /> <br /> The model is placed in a 3/4-open test section (only the floor is present). No indication on the homogeneity of the flow is given.<br /> <br /> Special attention should be given on the presence of a ground plate between the tunnel floor and the body. This plate is used for preventing wind tunnel boundary layer parasitic effects on the model. The model lies 50 mm above it and is placed on stilts of 30 mm diameter.<br /> <br /> =='''Flow Physics and Fluid Dynamics Data'''==<br /> <br /> The flow has no special characteristics. Air at ambiant conditions is used. The model is supposed to be smooth.<br /> <br /> © copyright ERCOFTAC 2004<br /> <br /> ----<br /> <br /> <br /> Contributors: Remi Manceau; Jean-Paul Bonnet - Université de Poitiers<br /> <br /> Site Design and Implementation: [[Atkins]] and [[UniS]]<br /> <br /> {{AC|front=AC 1-05|description=Description_AC1-05|testdata=Test Data_AC1-05|cfdsimulations=CFD Simulations_AC1-05|evaluation=Evaluation_AC1-05|qualityreview=Quality Review_AC1-05|bestpractice=Best Practice Advice_AC1-05|relatedUFRs=Related UFRs_AC1-05}}</div> Mike https://kbwiki.ercoftac.org/w/index.php?title=Abstr:Ahmed_body&diff=45192 Abstr:Ahmed body 2024-02-09T09:31:05Z <p>Mike: </p> <hr /> <div>{{AC|front=AC 1-05|description=Description_AC1-05|testdata=Test Data_AC1-05|cfdsimulations=CFD Simulations_AC1-05|evaluation=Evaluation_AC1-05|qualityreview=Quality Review_AC1-05|bestpractice=Best Practice Advice_AC1-05|relatedUFRs=Related UFRs_AC1-05}}<br /> <br /> == Application Area 1: External Aerodynamics ==<br /> <br /> === Application Challenge AC1-05 ===<br /> <br /> <br /> <br /> ==== Abstract ====<br /> A basic ground vehicle type of bluff body is investigated. The body consists of three parts: a fore body, a mid section and a rear end.<br /> <br /> Two experiments are available:<br /> <br /> A first one (Exp1) is performed at DLR-Göttingen in a wind tunnel at a significant Reynolds number (4.9 million for 60 m/s). The model is mounted near the wall of the wind tunnel, such that a ground effect is present. However, a ground plate is placed between the model and the floor of the wind tunnel in order to minimize this effect. The angle of the rear end slope is adjustable, between 0 and 40&amp;deg; with a 5&amp;deg; step. More details are available for angles of 5, 12.5 and 30&amp;deg;. About 210 pressure locations are available on the fore body, 83 in the mid section and 450 on rear ends. Wall flow visualizations are available. Detailed wake surveys are performed with 10 holes probes. Drag measurements are provided.<br /> <br /> A second, more recent experiment (Exp2) is provided by the Erlangen LSTM lab within the MOVA “Models for Vehicle Aerodynamics” European project (TU Delft, Univ. Of Manchester UMIST, LSTM, Electricité de France, AVL List, PSA Peugeot-Citroën). It concerns the same model as in the Ahmed study, running at 40m/s. Two-component LDV is used. Hot wire measurements are performed at 0.38 model length upstream of the model and in the boundary layer. Mean values and turbulence measurements (second and third order moments) are provided for 25&amp;deg; and 35&amp;deg; slant angle. 7,500 discrete positions are provided lying on 13 unique planes. Pressure measurements are performed on the rear part of the model.<br /> <br /> The basic shape of the so-called &amp;ldquo;Ahmed body&amp;rdquo; contains all the important features of real road vehicles: a main body, followed by a fully separated region. Prediction of separated flows is one of the more difficult task of CFD. The parametric variation of the angle of the rear part permits the simulation of various configurations relevant to real car characteristics. The complex 3D wake structure is also a challenging problem for CFD. This data base also contains drag results that are essential to prediction for practical purposes. The influence of turbulence models as well as the influence of the mesh and numerical scheme can then be tested at several levels: wall pressure, wake structure and force drag.<br /> <br /> The second set of experiments provides complementary results concerning the turbulent quantities that will be useful for a detailed analysis of turbulence models.<br /> <br /> The Design and Assessment parameters (DOAP's) for judging a CFD simulation are for this case as follows:<br /> <br /> *The first DOAP is clearly the drag coefficient computed for several slant angles.<br /> <br /> *A second DOAP is the topology of the flow, particularly the wall streamlines. Comparisons between computations and flow pattern from visualizations on the slant part will be useful. The structure of the flow will also be analyzed from the 3D representations in order to visualize the vortices.<br /> <br /> *A third DOAP will be the static pressure distributions.<br /> <br /> *A fourth DOAP will be the mean velocity distributions at several locations around and downstream of the body.<br /> <br /> *Lastly, the turbulent quantities can be considered as a DOAP; this however is more a guide for modelling than for a direct validation of codes.<br /> <br /> The Ahmed body configuration was a test case for 2 ERCOFTAC-IAHR workshops ( 2001 in Darmstadt and 2002 in Poitiers) and CFD results from 15 teams obtained for these workshops with various simple and more advanced RANS models and one LES are reported in the original test-case version produced in 2004. An update was provided in 2024 by F.R. Menter by adding results with accompanying documentation for the 25° slant- angle case based on the Menter et al (2024) paper.<br /> <br /> ==Reference==<br /> Menter, F.R., Hüppe, A., Flad D., Garbaruk A.V., Matyushenko A:A:, Stabnikov A:S: Large eddy simulations for the Ahmed car at 25° slant angle at different Reynolds numbers. Flow, Turbulence and Combustion, 112, 321-343, (2024).<br /> <br /> <br /> &lt;br&gt;<br /> &lt;br&gt;<br /> ----<br /> ''Contributors: Remi Manceau; Jean-Paul Bonnet - Université de Poitiers. Update (2024) F.R.Menter, ANSYS Germany'', <br /> <br /> {{AC|front=AC 1-05|description=Description_AC1-05|testdata=Test Data_AC1-05|cfdsimulations=CFD Simulations_AC1-05|evaluation=Evaluation_AC1-05|qualityreview=Quality Review_AC1-05|bestpractice=Best Practice Advice_AC1-05|relatedUFRs=Related UFRs_AC1-05}}</div> Mike https://kbwiki.ercoftac.org/w/index.php?title=DNS_1-5_Statistical_Data&diff=44927 DNS 1-5 Statistical Data 2023-10-10T12:39:44Z <p>Mike: Update data urls to account for + signs</p> <hr /> <div>=HiFi-TURB-DLR rounded step=<br /> {{DNSHeader<br /> |area=1<br /> |number=5<br /> }}<br /> __TOC__<br /> = Statistical data =<br /> In this section the relevant statistical data for the flow on the smooth bump computed with MIGALE is given. The reported data is the one mentioned in Table 1 of the [https://kbwiki-images.s3.amazonaws.com/8/80/List_of_desirable_and_minimum_quantities_to_be_entered_into_the_KB_Wiki.pdf list of desirable quantities (PDF)].<br /> <br /> The data is available as:<br /> * In .vtk (ASCII) format as statistical data (mid-span plane).<br /> * In .vtu (ASCII) format for instantaneous data.<br /> * In .csv (text) format as vertical profiles at various x-positions.<br /> <br /> ==Midplane data==<br /> Data of the statistics computed at the midspan of the computational domain are provided here. Statistics at the midspan are virtually the same for any other parallel plane. For more information regarding the stored quantities and the storage format, please refer to the [[DNS_1-5_format#Instantaneous_data_format|storage format guidelines]].<br /> <br /> The available files are:<br /> * [https://kbwiki-data.s3-eu-west-2.amazonaws.com/DNS-1/5/1_averaged_pressure.tar.gz averaged pressure (20.4 MB)].<br /> * [https://kbwiki-data.s3-eu-west-2.amazonaws.com/DNS-1/5/2_averaged_velocity_x.tar.gz averaged velocity x (21.9 MB)].<br /> * [https://kbwiki-data.s3-eu-west-2.amazonaws.com/DNS-1/5/3_averaged_velocity_y.tar.gz averaged velocity y (22.8 MB)].<br /> * [https://kbwiki-data.s3-eu-west-2.amazonaws.com/DNS-1/5/4_averaged_velocity_z.tar.gz averaged velocity z (23.2 MB)].<br /> * [https://kbwiki-data.s3-eu-west-2.amazonaws.com/DNS-1/5/5_Reynolds_stress_xx.tar.gz Reynolds stress xx (22.8 MB)].<br /> * [https://kbwiki-data.s3-eu-west-2.amazonaws.com/DNS-1/5/6_Reynolds_stress_yx.tar.gz Reynolds stress yx (22.9 MB)].<br /> * [https://kbwiki-data.s3-eu-west-2.amazonaws.com/DNS-1/5/7_Reynolds_stress_yy.tar.gz Reynolds stress yy (22.8 MB)].<br /> * [https://kbwiki-data.s3-eu-west-2.amazonaws.com/DNS-1/5/8_Reynolds_stress_zx.tar.gz Reynolds stress zx (23.3 MB)].<br /> * [https://kbwiki-data.s3-eu-west-2.amazonaws.com/DNS-1/5/9_Reynolds_stress_zy.tar.gz Reynolds stress zy (23.5 MB)].<br /> * [https://kbwiki-data.s3-eu-west-2.amazonaws.com/DNS-1/5/10_Reynolds_stress_zz.tar.gz Reynolds stress zz (22.9 MB)].<br /> * [https://kbwiki-data.s3-eu-west-2.amazonaws.com/DNS-1/5/11_Taylor_microscale.tar.gz Taylor microscale (22.6 MB)].<br /> * [https://kbwiki-data.s3-eu-west-2.amazonaws.com/DNS-1/5/12_Kolmogorov_length_scale.tar.gz Kolmogorov length scale (22.6 MB)].<br /> * [https://kbwiki-data.s3-eu-west-2.amazonaws.com/DNS-1/5/13_Kolmogorov_time_scale.tar.gz Kolmogorov time scale (22.7 MB)].<br /> <br /> ==Profile data==<br /> Profile data have been extracted at different streamwise locations (&lt;math&gt;x/H=-11,-10,-9,-8,-7,-6,-5,-4,-3,-2,-1,-0,0.5,0.75,1,1.25,1.5,1.75,2,2.25,2.5,2.75,3,3.25,3.5,4,4.5,5,6,7,8,9,10,12,14&lt;/math&gt;) and made dimensionless with respect to reference quantities (&lt;math&gt;u_{ref}&lt;/math&gt;, &lt;math&gt;\rho_{ref}&lt;/math&gt;, &lt;math&gt;p_{s,ref}&lt;/math&gt;, see [[UFR_3-36_Test_Case#table2|UFR 3-36: Table 2]]).<br /> The data stored in each file are:<br /> * streamwise location &lt;math&gt;x/H&lt;/math&gt;<br /> * vertical location &lt;math&gt;y/H&lt;/math&gt;<br /> * wall distance &lt;math&gt;(y-y_{wall})/H&lt;/math&gt;<br /> * average pressure &lt;math&gt;p/p_{s,ref}&lt;/math&gt;<br /> * average velocity components &lt;math&gt;U_{i}/u_{ref}&lt;/math&gt;<br /> * Reynolds stress components &lt;math&gt;R_{ij}/(\rho_{ref}u_{ref}^{2})&lt;/math&gt;<br /> * turbulent kinetic energy &lt;math&gt;k/u_{ref}^{2}&lt;/math&gt;<br /> <br /> Profiles at selected streamwise locations are reported in [[DNS_1-5_statistical#figure11|Fig. 11]].<br /> <br /> {|align=&quot;center&quot; border=&quot;1&quot; cellpadding=&quot;5&quot;<br /> |-<br /> |[https://kbwiki-data.s3-eu-west-2.amazonaws.com/DNS-1/5/profile_uDNS_-11.00.csv profile_uDNS_-11.00.csv] <br /> |-<br /> |[https://kbwiki-data.s3-eu-west-2.amazonaws.com/DNS-1/5/profile_uDNS_-10.00.csv profile_uDNS_-10.00.csv] <br /> |-<br /> |[https://kbwiki-data.s3-eu-west-2.amazonaws.com/DNS-1/5/profile_uDNS_-09.00.csv profile_uDNS_-09.00.csv] <br /> |-<br /> |[https://kbwiki-data.s3-eu-west-2.amazonaws.com/DNS-1/5/profile_uDNS_-08.00.csv profile_uDNS_-08.00.csv] <br /> |-<br /> |[https://kbwiki-data.s3-eu-west-2.amazonaws.com/DNS-1/5/profile_uDNS_-07.00.csv profile_uDNS_-07.00.csv] <br /> |-<br /> |[https://kbwiki-data.s3-eu-west-2.amazonaws.com/DNS-1/5/profile_uDNS_-06.00.csv profile_uDNS_-06.00.csv] <br /> |-<br /> |[https://kbwiki-data.s3-eu-west-2.amazonaws.com/DNS-1/5/profile_uDNS_-05.00.csv profile_uDNS_-05.00.csv] <br /> |-<br /> |[https://kbwiki-data.s3-eu-west-2.amazonaws.com/DNS-1/5/profile_uDNS_-04.00.csv profile_uDNS_-04.00.csv] <br /> |-<br /> |[https://kbwiki-data.s3-eu-west-2.amazonaws.com/DNS-1/5/profile_uDNS_-03.00.csv profile_uDNS_-03.00.csv] <br /> |-<br /> |[https://kbwiki-data.s3-eu-west-2.amazonaws.com/DNS-1/5/profile_uDNS_-02.00.csv profile_uDNS_-02.00.csv] <br /> |-<br /> |[https://kbwiki-data.s3-eu-west-2.amazonaws.com/DNS-1/5/profile_uDNS_-01.00.csv profile_uDNS_-01.00.csv] <br /> |-<br /> |[https://kbwiki-data.s3-eu-west-2.amazonaws.com/DNS-1/5/profile_uDNS_-00.00.csv profile_uDNS_-00.00.csv] <br /> |-<br /> |[https://kbwiki-data.s3-eu-west-2.amazonaws.com/DNS-1/5/profile_uDNS_%2B00.50.csv profile_uDNS_+00.50.csv] <br /> |-<br /> |[https://kbwiki-data.s3-eu-west-2.amazonaws.com/DNS-1/5/profile_uDNS_%2B00.75.csv profile_uDNS_+00.75.csv] <br /> |-<br /> |[https://kbwiki-data.s3-eu-west-2.amazonaws.com/DNS-1/5/profile_uDNS_%2B01.00.csv profile_uDNS_+01.00.csv]<br /> |-<br /> |[https://kbwiki-data.s3-eu-west-2.amazonaws.com/DNS-1/5/profile_uDNS_%2B01.25.csv profile_uDNS_+01.25.csv] <br /> |-<br /> |[https://kbwiki-data.s3-eu-west-2.amazonaws.com/DNS-1/5/profile_uDNS_%2B01.50.csv profile_uDNS_+01.50.csv] <br /> |-<br /> |[https://kbwiki-data.s3-eu-west-2.amazonaws.com/DNS-1/5/profile_uDNS_%2B01.75.csv profile_uDNS_+01.75.csv] <br /> |-<br /> |[https://kbwiki-data.s3-eu-west-2.amazonaws.com/DNS-1/5/profile_uDNS_%2B02.00.csv profile_uDNS_+02.00.csv] <br /> |-<br /> |[https://kbwiki-data.s3-eu-west-2.amazonaws.com/DNS-1/5/profile_uDNS_%2B02.25.csv profile_uDNS_+02.25.csv] <br /> |-<br /> |[https://kbwiki-data.s3-eu-west-2.amazonaws.com/DNS-1/5/profile_uDNS_%2B02.50.csv profile_uDNS_+02.50.csv] <br /> |-<br /> |[https://kbwiki-data.s3-eu-west-2.amazonaws.com/DNS-1/5/profile_uDNS_%2B02.75.csv profile_uDNS_+02.75.csv] <br /> |-<br /> |[https://kbwiki-data.s3-eu-west-2.amazonaws.com/DNS-1/5/profile_uDNS_%2B03.00.csv profile_uDNS_+03.00.csv] <br /> |-<br /> |[https://kbwiki-data.s3-eu-west-2.amazonaws.com/DNS-1/5/profile_uDNS_%2B03.25.csv profile_uDNS_+03.25.csv] <br /> |-<br /> |[https://kbwiki-data.s3-eu-west-2.amazonaws.com/DNS-1/5/profile_uDNS_%2B03.50.csv profile_uDNS_+03.50.csv] <br /> |-<br /> |[https://kbwiki-data.s3-eu-west-2.amazonaws.com/DNS-1/5/profile_uDNS_%2B04.00.csv profile_uDNS_+04.00.csv]<br /> |-<br /> |[https://kbwiki-data.s3-eu-west-2.amazonaws.com/DNS-1/5/profile_uDNS_%2B04.50.csv profile_uDNS_+04.50.csv] <br /> |-<br /> |[https://kbwiki-data.s3-eu-west-2.amazonaws.com/DNS-1/5/profile_uDNS_%2B05.00.csv profile_uDNS_+05.00.csv] <br /> |-<br /> |[https://kbwiki-data.s3-eu-west-2.amazonaws.com/DNS-1/5/profile_uDNS_%2B06.00.csv profile_uDNS_+06.00.csv] <br /> |-<br /> |[https://kbwiki-data.s3-eu-west-2.amazonaws.com/DNS-1/5/profile_uDNS_%2B07.00.csv profile_uDNS_+07.00.csv] <br /> |-<br /> |[https://kbwiki-data.s3-eu-west-2.amazonaws.com/DNS-1/5/profile_uDNS_%2B08.00.csv profile_uDNS_+08.00.csv] <br /> |-<br /> |[https://kbwiki-data.s3-eu-west-2.amazonaws.com/DNS-1/5/profile_uDNS_%2B09.00.csv profile_uDNS_+09.00.csv] <br /> |-<br /> |[https://kbwiki-data.s3-eu-west-2.amazonaws.com/DNS-1/5/profile_uDNS_%2B10.00.csv profile_uDNS_+10.00.csv] <br /> |-<br /> |[https://kbwiki-data.s3-eu-west-2.amazonaws.com/DNS-1/5/profile_uDNS_%2B12.00.csv profile_uDNS_+12.00.csv] <br /> |-<br /> |[https://kbwiki-data.s3-eu-west-2.amazonaws.com/DNS-1/5/profile_uDNS_%2B14.00.csv profile_uDNS_+14.00.csv] <br /> |}<br /> &lt;br/&gt;<br /> <br /> &lt;div id=&quot;figure11&quot;&gt;&lt;/div&gt;<br /> {|align=&quot;center&quot; border=&quot;0&quot; width=&quot;600&quot;<br /> |[[Image:DNS1-5 rounded step y u.png|600px]]<br /> |-<br /> |[[Image:DNS1-5 rounded step y v.png|600px]]<br /> |-<br /> |[[Image:DNS1-5 rounded step y Rexx.png|600px]]<br /> |-<br /> |[[Image:DNS1-5 rounded step y Reyy.png|600px]]<br /> |-<br /> |[[Image:DNS1-5 rounded step y Rezz.png|600px]]<br /> |-<br /> |[[Image:DNS1-5 rounded step y k.png|600px]]<br /> |-<br /> |[[Image:DNS1-5 rounded step y Reyx.png|600px]]<br /> |-<br /> !align=&quot;center&quot;|Figure 11: HiFi-TURB-DLR rounded step, profiles at selected stremwise locations <br /> |}<br /> &lt;br/&gt;<br /> <br /> ==Contour data==<br /> Contour data of averaged velocity components and Reynolds stresses is also provided in [[DNS_1-5_statistical#figure12|Fig. 12]].<br /> Reynolds stresses show an intensity peak which moves away from the wall as the flow moves above the rounded step.<br /> Downstream the step, however, such peak gets closer to the wall as the boundary layer is recovering the canonical behaviour for a zero pressure gradient configuration.<br /> <br /> &lt;div id=&quot;figure12&quot;&gt;&lt;/div&gt;<br /> {|align=&quot;center&quot; border=&quot;0&quot; width=&quot;900&quot;<br /> |[[Image:DNS1-5 rounded step u contour.png|900px]]<br /> |-<br /> |[[Image:DNS1-5 rounded step v contour.png|900px]]<br /> |-<br /> |[[Image:DNS1-5 rounded step R_xx contour.png|900px]]<br /> |-<br /> |[[Image:DNS1-5 rounded step R_yy contour.png|900px]]<br /> |-<br /> |[[Image:DNS1-5 rounded step R_zz contour.png|900px]]<br /> |-<br /> |[[Image:DNS1-5 rounded step R_yx contour.png|900px]]<br /> |-<br /> !align=&quot;center&quot;|Figure 12: HiFi-TURB-DLR rounded step, contours of averaged velocity components and Reynolds stresses <br /> |}<br /> &lt;br/&gt;<br /> <br /> ==Additional data==<br /> The following averaged quantities are provided along the solid wall:<br /> * the pressure coefficient &lt;math&gt;C_p&lt;/math&gt;<br /> * the skin friction coefficient &lt;math&gt;C_f&lt;/math&gt;<br /> <br /> The pressure coefficient is defined as &lt;math&gt;C_{p}=2(p-p_{chk})/(\rho_{ref} u_{ref}^2)&lt;/math&gt;, where <br /> &lt;math&gt;p_{chk}&lt;/math&gt; is the pressure at wall at the checkpoint &lt;math&gt;x/H=-3.5&lt;/math&gt;, while the skin friction coefficient is defined as &lt;math&gt;C_{f}=2(\tau_{wall})/(\rho_{ref} u_{ref}^2)&lt;/math&gt;. &lt;math&gt;u_{ref}&lt;/math&gt; and &lt;math&gt;\rho_{ref}&lt;/math&gt; are the velocity and density at the reference conditions (see [[UFR_3-36_Test_Case#table2|UFR 3-36: Table 2]]), respectively.<br /> Both coefficients have been obtained by averaging along the span direction the time averaged solution.<br /> <br /> {|align=&quot;center&quot; border=&quot;1&quot; cellpadding=&quot;5&quot;<br /> | [https://kbwiki-data.s3-eu-west-2.amazonaws.com/DNS-1/5/wall_dns.csv wall_dns.csv] <br /> |}<br /> <br /> &lt;div id=&quot;figure13&quot;&gt;&lt;/div&gt;<br /> {|align=&quot;center&quot; border=&quot;0&quot; width=&quot;550&quot;<br /> |[[Image:DNS1-5 Rounded step Cp.png|370px]]||[[Image:DNS1-5 Rounded step Cf.png|370px]]<br /> |-<br /> !align=&quot;center&quot; colspan=&quot;2&quot;|Figure 13: HiFi-TURB-DLR rounded step, pressure and skin friction coefficients on the solid wall <br /> |}<br /> &lt;br/&gt;<br /> <br /> ----<br /> {{ACContribs<br /> | authors=Francesco Bassi, Alessandro Colombo, Francesco Carlo Massa<br /> | organisation=Università degli studi di Bergamo (UniBG)<br /> }}<br /> {{DNSHeader<br /> |area=1<br /> |number=5<br /> }}<br /> <br /> <br /> © copyright ERCOFTAC {{CURRENTYEAR}}</div> Mike https://kbwiki.ercoftac.org/w/index.php?title=Template:DNSHeader&diff=44897 Template:DNSHeader 2023-09-27T11:56:02Z <p>Mike: Protected &quot;Template:DNSHeader&quot; ([Edit=Allow only administrators] (indefinite) [Move=Allow only administrators] (indefinite))</p> <hr /> <div>&lt;noinclude&gt;<br /> This template is used for defining the links at the top of each DNS page.<br /> <br /> Parameters:<br /> * area - the app area number (1,2,3..)<br /> * number- the article number (01,02,03,...)<br /> &lt;/noinclude&gt;<br /> &lt;table class=&quot;myLinksTable&quot;&gt;<br /> &lt;tr&gt;<br /> &lt;td&gt;<br /> [[DNS_{{{area}}}-{{{number}}}|Front Page]]<br /> &lt;/td&gt;<br /> &lt;td&gt;<br /> [[DNS_{{{area}}}-{{{number}}}_Description|Description]] <br /> &lt;/td&gt;<br /> &lt;td&gt;<br /> [[DNS_{{{area}}}-{{{number}}}_Computational_Details|Computational Details]] <br /> &lt;/td&gt;<br /> &lt;td&gt;<br /> [[DNS_{{{area}}}-{{{number}}}_Quantification_of_Resolution| Quantification of Resolution]] <br /> &lt;/td&gt;<br /> &lt;td&gt;<br /> [[DNS_{{{area}}}-{{{number}}}_Statistical_Data|Statistical Data]] <br /> &lt;/td&gt;<br /> &lt;td&gt;<br /> [[DNS_{{{area}}}-{{{number}}}_Instantaneous_Data|Instantaneous Data]] <br /> &lt;/td&gt;<br /> &lt;td&gt;<br /> [[DNS_{{{area}}}-{{{number}}}_Storage_Format|Storage Format]] <br /> &lt;/td&gt;<br /> &lt;/tr&gt;<br /> &lt;/table&gt;</div> Mike https://kbwiki.ercoftac.org/w/index.php?title=News&diff=44762 News 2023-08-17T10:06:44Z <p>Mike: </p> <hr /> <div>__NOTOC__<br /> &lt;div id=&quot;contents&quot;&gt;&lt;/div&gt;<br /> <br /> ==August 2023: New EXP case added to wiki==<br /> A new EXP case (EXP1-4) [[EXP_1-4|Axisymmetric drop impact dynamics on a wall film of the same liquid]] is now available in the [[EXP_Index| EXP]] section.<br /> <br /> ==August 2023: New EXP case added to wiki==<br /> A new EXP case (EXP1-1) [[EXP_1-1|Pressure-swirl spray in a low-turbulence cross-flow]] is now available in the [[EXP_Index| EXP]] section.<br /> <br /> ==August 2023: First EXP case added to wiki==<br /> The first EXP case has now been added to the wiki. (EXP1-2) [[EXP_1-2|Pollutant transport between a street canyon and a 3D urban array as a function of wind direction and roof height non-uniformity]] is now available in the [[EXP_Index| EXP]] section.<br /> <br /> ==February 2023: New DNS case added to wiki==<br /> A new DNS case (DNS1-6) [[DNS_1-6|3D wing-body junction]] is now available in the [[DNS_Index| DNS]] section.<br /> <br /> ==February 2023: New DNS case added to wiki==<br /> A new DNS case (DNS1-5) [[DNS_1-5|HiFi-TURB-DLR rounded step]] is now available in the [[DNS_Index| DNS]] section.<br /> <br /> ==February 2023: New UFR added to wiki==<br /> A new UFR (UFR3-36) [[UFR_3-36|HiFi-TURB-DLR rounded step]] has been added to the Semi-confined flows section.<br /> <br /> ==January 2023: New AC added to wiki==<br /> A new AC (AC7-03) [[AC7-03|Flow in a Ventricular Assist Device - Pump Performance &amp; Blood Damage Prediction]] has been added to the Biomedical Flows section.<br /> <br /> ==January 2023: New DNS case added to wiki==<br /> A new DNS case (DNS1-3) [[DNS_1-3|Flow in a 3D diffuser]] is now available in the [[DNS_Index| DNS]] section.<br /> <br /> ==January 2023: First DNS case added to wiki==<br /> The first DNS case has now be added to the wiki. (DNS1-2) [[DNS_1-2|DNS Channel Flow]] is now available in the [[DNS_Index| DNS]] section.<br /> <br /> ==January 2022: New AC added to wiki==<br /> A new AC (AC7-04) [[AC7-04|A pulsatile 3D flow relevant to thoracic hemodynamics: CFD - 4D Flow MRI comparison]] has been added to the Biomedical Flows section.<br /> <br /> ==November 2020: New UFR added to wiki==<br /> A new UFR (UFR3-35) [[UFR_3-35|Cylinder-wall junction flow]] has been added to the Semi-confined flows section.<br /> <br /> ==June 2020: New AC added to wiki==<br /> A new AC (AC7-02) [[AC7-02|Airflow in the human upper airways]] has been added to the biomedical flows section.<br /> <br /> ==October 2019: New AC added to new wiki section==<br /> A new section &quot;Biomedical Flows&quot; has been added to the wiki, with a new AC (AC7-01)<br /> [[AC7-01|Aerosol deposition in the human upper airways]].<br /> <br /> ==August 2019: New AC added to wiki==<br /> A new AC (AC2-12) [[AC2-12|Turbulent separated inert and reactive flows over a triangular bluff body]] has been added to the combustion section.<br /> <br /> ==February 2019: New AC added to wiki==<br /> A new AC (AC6-15) [[AC6-15|Vortex ropes in draft tube of a laboratory Kaplan hydro turbine at low load]] has been added to the turbomachinery section.<br /> <br /> ==November 2018: New AC added to wiki==<br /> A new AC (AC2-11) [[AC2-11|Delft-Jet-in-Hot-Coflow (DJHC) burner]] has been added to the combustion section.<br /> <br /> ==November 2018: New AC added to wiki==<br /> A new AC (AC2-10) [[AC2-10|Internal combustion engine flows for motored operation]] has been added to the combustion section.<br /> <br /> ==March 2018: New UFR added to wiki==<br /> A new UFR (UFR3-34) [[UFR_3-34|Smooth wall separation and reattachment at high Reynolds numbers]] has been added to the Semi-confined flows section.<br /> <br /> ==March 2018: New UFR added to wiki==<br /> A new UFR (UFR4-20) [[UFR_4-20|Mixing ventilation flow in an enclosure driven by a transitional wall jet]] has been added to the Confined flows section.<br /> <br /> ==July 2017: Old Wiki Switched Off==<br /> The wiki should now be regarded as being out of beta-test and fully usable. The old wiki has been discontinued.<br /> <br /> ==May 2017: New KB Wiki Launched==<br /> The wiki now has all content available to everybody without the need to log in. The distinction between Gold, Silver and Silver-plus articles has been removed.<br /> <br /> This wiki is now hosted on newer hardware with more up-to-date software. It should be regarded as being in Beta-test until the end of May 2017, when the old server will be switched off. If there are any difficulties encountered, the old site can be accessed via the link in green text at the top of each page. Please direct any queries to the administrator at ellacott@ellacott.plus.com.<br /> <br /> ==August 2016: New AC added to wiki==<br /> A new AC (AC6-14) [[AC6-14|Swirling flow in a conical diffuser generated with rotor-stator interaction]] has been added to the Turbomachinery internal flow section in the &quot;Silver Star&quot; category.<br /> <br /> ==April 2016: New UFR added to wiki==<br /> A new UFR (UFR4-19) [[UFR_4-19|Converging-diverging transonic diffuser]] has been added to the Confined flows section in the &quot;Silver Star&quot; category.<br /> <br /> ==April 2016: New UFR added to wiki==<br /> A new UFR (UFR3-33) [[UFR_3-33|Turbulent flow past a wall-mounted hemisphere]] has been added to the Semi-confined flows section in the &quot;Silver Star&quot; category.<br /> <br /> ==December 2015: New UFR added to Wiki==<br /> A new UFR (UFR4-18) [[UFR_4-18|Flow and heat transfer in a pin-fin array]] has been added to the Confined Flows section in the &quot;Silver Star&quot; category.<br /> <br /> ==July 2015: New AC added to Wiki==<br /> A new AC (AC1-09) [[AC1-09|Vortex breakdown above a delta wing with sharp leading edge]] has been added to the External Aerodynamics section in the &quot;Silver Star&quot; category.<br /> <br /> ==June 2014: New UFR added to Wiki==<br /> A new UFR (UFR2-14) [[UFR_2-14|Fluid-structure interaction in turbulent flow past cylinder/plate configuration II]] has been added to the Flows Around Bodies section in the &quot;Silver Star&quot; category.<br /> <br /> ==May 2014: New UFR added to Wiki==<br /> A new UFR (UFR2-15) [[UFR_2-15|Benchmark on the Aerodynamics of a Rectangular 5:1 Cylinder (BARC)]] has been added to the Flows<br /> Around Bodies section in the &quot;Silver&quot; category.<br /> <br /> ==December 2013: New UFR added to Wiki==<br /> A new UFR (UFR2-13) [[UFR_2-13|Fluid-structure interaction in turbulent flow past cylinder/plate configuration I]] has been added to the Flows Around Bodies section in the &quot;Silver Star&quot; category.<br /> <br /> ==November 2013: New UFR added to Wiki==<br /> A new UFR (UFR3-32) [[UFR_3-32|Planar shock-wave boundary-layer interaction]] has been added to the Semi-Confined Flows section in the &quot;Silver Star&quot; category.<br /> ==July 2013: Enhancements to UFR3-30 2D Periodic Hill Flow==<br /> Links to results of and documentation on test calculations performed in the European ATAAC project are now included.<br /> <br /> ==May 2013: Enhancements to UFR4-16 Flow in a 3D diffuser==<br /> Links to results of and documentation on test calculations performed in the European ATAAC project are now included.<br /> <br /> ==March 2013: New AC added to Wiki==<br /> A new AC (AC3-12) [[AC3-12|Particle-laden swirling flow]] has been added to the Chemical, Process, Thermal and Nuclear Safety section in the &quot;Silver Star&quot; category.<br /> <br /> ==November 2012: New UFR added to Wiki==<br /> A new UFR (UFR2-12) [[UFR_2-12|Turbulent Flow Past Two-Body Configurations]] has been added to the Flows Around Bodies section in the &quot;Silver Star&quot; category.<br /> <br /> ==September 2012: New UFR added to Wiki==<br /> A new UFR (UFR4-16) [[UFR_4-16|Flow in a 3D diffuser]] has been added to the Confined Flows section in the &quot;Silver Star&quot; category.<br /> <br /> ==July 2012: New UFR added to Wiki==<br /> A new UFR (UFR3-31) [[UFR_3-31|Flow over curved backward-facing step]] has been added to the Semi-confined Flows section in the &quot;Silver Star&quot; category.<br /> <br /> ==September 2011: New UFR added to Wiki==<br /> A new UFR (UFR2-11) [[UFR_2-11|High Reynolds Number Flow around Airfoil in Deep Stall]] has been added to the Flows Around Bodies section in the &quot;Silver Star&quot; category.<br /> <br /> ==June 2011: New AC added to Wiki==<br /> A new AC (AC2-09) [[Sandia Flame D|&quot;Sandia Flame D&quot;]] has been added to the Combustion section in the &quot;Silver Star&quot; category.<br /> <br /> ==March 2011: New AC added to Wiki==<br /> A new AC (AC2-08) [[Premixed Methane-Air Swirl Burner (TECFLAM)|&quot;Premixed Methane-Air Swirl Burner (TECFLAM)&quot;]] has been added to the Combustion section in the &quot;Silver Star&quot; category.<br /> <br /> ==January 2011: New UFR added to Wiki==<br /> A new UFR (UFR2-10) [[Flow Around Finite-Height Circular Cylinder|&quot;Flow Around Finite-Height Circular Cylinder&quot;]] has been added to the Flows Around Bodies section in the &quot;Silver Star&quot; category.<br /> <br /> ==August 2010: Wiki Upgrade and New Server==<br /> We are now running MediaWiki 1.16.0 on a new Linux-based server.<br /> The opportunity is also being taken to upgrade other software components of the wiki in the interests of improving reliability and maintainability.<br /> <br /> ==July 2010: New UFR added to Wiki==<br /> A new UFR (UFR1-07) [[Abstr:Unsteady near-field plume|&quot;Unsteady near-field plume&quot;]]<br /> has been added to the Free Flows section in the &quot;Silver Star&quot; category.<br /> <br /> ==April 2010: New UFR added to Wiki==<br /> A new UFR (UFR1-06) [[Axisymmetric buoyant far-field plume|&quot;Axisymmetric bouyant far-field plume&quot;]]<br /> has been added to the Free Flows section in the &quot;Silver Star&quot; category.<br /> <br /> ==March 2010: New UFR added to Wiki==<br /> A new UFR (UFR3-30) [[2D Periodic Hill Flow|&quot;2D Periodic Hill Flow&quot;]]<br /> has been added to the Semi-confined Flows section in the &quot;Silver Star&quot; category.<br /> <br /> ==January 2010: Wiki Forums Launched==<br /> A user &lt;span class=&quot;plainlinks&quot;&gt;[http://qnet-ercoftac.cfms.org.uk/31frm46 forum]&lt;/span&gt; associated with this wiki has now been launched.<br /> It is intended that this will be the primary channel for queries, feedback and comment.</div> Mike https://kbwiki.ercoftac.org/w/index.php?title=EXP_Index&diff=44759 EXP Index 2023-08-17T10:03:14Z <p>Mike: </p> <hr /> <div>== Experimental Studies Index == <br /> <br /> {| class=&quot;wikitable&quot;<br /> |+ EXP Library<br /> ! EXP !! Title !! Contributor !! Organisation<br /> |-<br /> | EXP 1-1 || [[EXP 1-1| Pressure-swirl spray in a low-turbulence cross-flow ]] || Ondrej Cejpek, Milan Maly, Jan Jedelsky, Ondrej Hajek || Brno University of Technology<br /> |-<br /> | EXP 1-2 || [[EXP 1-2| Pollutant transport between a street canyon and a 3D urban array as a function of wind direction and roof height non-uniformity ]] || Stepan Nosek || Institute of Thermomechanics of the CAS<br /> |-<br /> | EXP 1-4 || [[EXP 1-4| Axisymmetric drop impact dynamics on a wall film of the same liquid ]] || Milad Bagheri, Bastian Stumpf, Ilia V. Roisman, Cameron Tropea, Jeanette Hussong, Martin Wörner, Holger Marschall || Technical University of Darmstadt and Karlsruhe Institute of Technology<br /> <br /> |}</div> Mike https://kbwiki.ercoftac.org/w/index.php?title=EXP_1-4_Measurement_Data_and_Results&diff=44758 EXP 1-4 Measurement Data and Results 2023-08-17T10:01:56Z <p>Mike: </p> <hr /> <div><br /> =Axisymmetric drop impact dynamics on a wall film of the same liquid=<br /> {{EXPHeader<br /> |area=1<br /> |number=4<br /> }}<br /> __NOTOC__<br /> = Measurement data/results =<br /> <br /> The '''drop-film interaction in the three experimental videos''' (see Table 1 in Section [[EXP 1-4 Description]]) can be characterized as follows. <br /> <br /> * For the '''low energy impact''' the drop joins the liquid film smoothly without formation of a rim or crown. In this ''deposition regime'', the drop spreads on the surface of the liquid film forming a disk-shaped structure. In the late stage, capillary waves propagate on the surface of the film without formation of a notable central dome.<br /> <br /> * For the '''moderate energy impact''' a rising crown is formed at the boundary between the residual and the initial film where there is a kinematic discontinuity due to the jump in both the film thickness and the local velocity field. The crown ascend continues as long as the inertial forces dominate the surface tension forces. The upper free rim of the crown remains stable and fully axisymmetric and the case corresponds to the ''crown formation without break-up regime''. In the late stage after collapse of the crown, a dome like structure forms at the impact center without generation of a jet.<br /> <br /> * The case of the '''high energy impact''' corresponds to the ''crown formation without break-up regime'' as well. However, the increased magnitude of inertial forces causes the crown to grow much higher (approximately twice) as compared to the moderate energy impact. While the upper free rim remains axisymmetric during the ascend of the crown, slight deviations from axisymmetry can be noticed during the collapse of the crown. Moreover, the energy of the impact is high enough to form a central Worthington jet which emerges from the impact center. The central jet experiences rupture (pinch-off) and forms satellite droplets. These droplets bounce on the surface of the disturbed film before merging into it. <br /> <br /> The '''time evolution of the three characteristic crown dimensions''' in experiment and simulation is provided via Excel files for the moderate and high impact energy cases. These Excel files are available for download through the website https://tudatalib.ulb.tu-darmstadt.de/handle/tudatalib/3295.2. The data in the Excel file for the case with moderate impact energy are displayed in Fig. 7. There, experimental results for the three crown dimensions (base diameter, rim diameter, crown height) are compared with numerical results obtained for the two surface tension models and different grid resolutions. The Excel file includes one worksheet for each of the six subfigures of Fig. 7. Each of the six worksheets contains one column for time, one column for the respective experimental crown dimension and four columns for the respective numerical results obtained with the different resolutions. <br /> <br /> <br /> [[File:TRR150-Fig_Profiles_2mps.png|870px|thumb|center|Fig. 7: Comparison of numerical results for the crown base diameter, crown rim diameter and crown height with the experiment - moderate energy impact.]]<br /> <br /> <br /> The content of the Excel file for the case with high impact energy is equivalent. An illustration similar to Fig. 7 for the high energy impact can be found in Bagheri et al. (2022), where also more detailed discussions of the experimental and numerical results are provided. It is concluded that the relaxation model for surface tension is able to reproduce the experimental data for all impact energies with reasonable accuracy irrespective of the number of interfacial cells, in contrast to the equilibrium model. <br /> <br /> M. Bagheri, B. Stumpf, I.V. Roisman, C. Tropea, J. Hussong, M. Wörner, H. Marschall, ''Interfacial relaxation – Crucial for phase-field methods to capture low to high energy drop-film impacts'', Int. J. Heat Fluid Flow 94 (2022) 108943, https://doi.org/10.1016/j.ijheatfluidflow.2022.108943<br /> <br /> &lt;br/&gt;<br /> ----<br /> {{ACContribs<br /> |authors=Milad Bagheri, Bastian Stumpf, Ilia V. Roisman, Cameron Tropea, Jeanette Hussong, Martin Wörner, Holger Marschall<br /> |organisation=Technical University of Darmstadt and Karlsruhe Institute of Technology<br /> }}<br /> {{EXPHeader<br /> |area=1<br /> |number=4<br /> }}<br /> <br /> <br /> © copyright ERCOFTAC {{CURRENTYEAR}}</div> Mike https://kbwiki.ercoftac.org/w/index.php?title=EXP_1-4_Data_Quality_and_Accuracy&diff=44757 EXP 1-4 Data Quality and Accuracy 2023-08-17T10:01:40Z <p>Mike: </p> <hr /> <div><br /> =Axisymmetric drop impact dynamics on a wall film of the same liquid=<br /> {{EXPHeader<br /> |area=1<br /> |number=4<br /> }}<br /> __NOTOC__<br /> = Data Quality and Accuracy of Measurements =<br /> <br /> For every set of parameters, experiments are repeated at least five<br /> times to minimize the effect of random errors. The impact parameters<br /> are verified in a post processing step, showing that the drop diameter of<br /> 1.5 mm is matched with a deviation of less than the resolution of the<br /> camera (31 μm). Also the target velocity is set precisely to 1.00 m/s,<br /> 1.99 m/s and 3.02 m/s with a relative error of less than ±1%. Due to the<br /> well-adjusted impact parameters, the formation of the corona and hence<br /> the temporal development of its geometrical dimensions show great<br /> repeatability. The mean relative standard deviation of the parameters<br /> ''d''&lt;sub&gt;CB&lt;/sub&gt;, ''d''&lt;sub&gt;CT&lt;/sub&gt; and ''h''&lt;sub&gt;C&lt;/sub&gt; is less than 0.45%, 1.41% and 2.23%, respectively. For<br /> the sake of clarity, average values of each data set are given without indicating the aforementioned standard deviation.<br /> <br /> &lt;br/&gt;<br /> ----<br /> {{ACContribs<br /> |authors=Milad Bagheri, Bastian Stumpf, Ilia V. Roisman, Cameron Tropea, Jeanette Hussong, Martin Wörner, Holger Marschall<br /> |organisation=Technical University of Darmstadt and Karlsruhe Institute of Technology<br /> }}<br /> {{EXPHeader<br /> |area=1<br /> |number=4<br /> }}<br /> <br /> <br /> © copyright ERCOFTAC {{CURRENTYEAR}}</div> Mike https://kbwiki.ercoftac.org/w/index.php?title=EXP_1-4_Measurement_Quantities_and_Techniques&diff=44756 EXP 1-4 Measurement Quantities and Techniques 2023-08-17T10:01:29Z <p>Mike: </p> <hr /> <div><br /> =Axisymmetric drop impact dynamics on a wall film of the same liquid=<br /> {{EXPHeader<br /> |area=1<br /> |number=4<br /> }}<br /> __NOTOC__<br /> <br /> = Measurement quantities and techniques=<br /> <br /> == Experiment ==<br /> <br /> When carrying out the experiments, a uniform film of 500 μm thickness is prepared utilizing the film thickness sensor. In the next step, the film thickness sensor is moved and a drop is generated. During the drop impact onto the liquid film shadowgraphy images are taken. A synchronized high-performance LED (Constellation 120E) in combination with a diffuser plate provides a uniform background illumination. Images are taken with a high-speed CMOS camera (Photron SA-X2), recording the impact at a frame rate of 20000 fps with a resolution of 31 μm/px. <br /> <br /> The dynamics of the drop-film interaction is characterized by three parameters as indicated in Fig. 4. <br /> * The crown diameter at the crown base ''d''&lt;sub&gt;CB&lt;/sub&gt;, measured 0.13 mm above the film surface<br /> * The crown diameter at the free rim forming the crown top ''d''&lt;sub&gt;CT&lt;/sub&gt;<br /> * The crown height ''h''&lt;sub&gt;C&lt;/sub&gt;<br /> These parameters are obtained from preprocessed images with the help of the<br /> MATLAB Image-Processing Toolbox. For this, a background subtraction<br /> from raw images is first performed to be able to distinguish the crown<br /> from the background. Then the images are binarised, using a global<br /> thresholding method, as shown on the left side of Fig. 4. From the<br /> evaluation of consecutive binarised images, the temporal evolution of<br /> ''d''&lt;sub&gt;CB&lt;/sub&gt;, ''d''&lt;sub&gt;CT&lt;/sub&gt; and ''h''&lt;sub&gt;C&lt;/sub&gt; can be determined. Reflections on the crown surface can<br /> lead to nonphysical interpretations of the crowns dimensions in individual<br /> frames. To eliminate erroneous values from the results, all values<br /> with a deviation of more than three standard deviations from a running<br /> median of 20 consecutive frames are considered as outlier.<br /> <br /> <br /> [[File:TRR150-Fig-ImageProcessing.png|800px|thumb|center|Fig. 4: Montage of binarized picture on the left and a raw picture on the right. The crown diameter at the free rim ''d''&lt;sub&gt;CT&lt;/sub&gt; and the crown diameter at the base ''d''&lt;sub&gt;CB&lt;/sub&gt; are depicted in red. The crown height ''h''&lt;sub&gt;C&lt;/sub&gt; is depicted in green. The dashed blue line indicates the film level.]]<br /> <br /> <br /> == Numerical method and computational setup ==<br /> <br /> The numerical simulations are performed with a diffuse-interface phase-field method which solves the coupled Cahn-Hilliard Navier-Stokes equations by a finite volume method using OpenFOAM (code ''phaseFieldFoam''). The computational setup is shown in Fig. 5. In OpenFOAM, axisymmetric calculations are realized by a wedge-shaped domain with small opening angle (Fig. 5 a). The domain size and the initial conditions are displayed in Fig. 5 (b). In the diffuse-interface region, the mesh is adaptive as illustrated in Fig. 5 (c) for the initial configuration. In the azimuthal direction, the wedge is discretized by one mesh cell. <br /> <br /> <br /> [[File:TRR150-Fig-Computational-Setup.png|1200px|thumb|center|Fig. 5: Illustration of a suitable computational setup: a) Wedge-shaped domain with boundary conditions, b) Domain size and initial phase distribution, c) Typical initial configuration of the adaptive grid.]]<br /> <br /> <br /> In the numerical simulations, two different models for the surface tension force (equilibrium/relaxation) are employed in combination with different spatial resolutions. In the phase field method, the surface tension force is related to the profile of the phase-discriminating order parameter (''C'') and depends in particular on the gradient of ''C'' within the diffuse interface region. In the standard (equilibrium) formulation, ''C'' is assumed to follow the tanh profile of the equilibrium state whereas the relaxation model accounts for the deviation of the actual profile of ''C'' from the equilibrium profile. The spatial resolution is quantified by the number of mesh cells ''N''&lt;sub&gt;c&lt;/sub&gt; used to resolve the thickness of the diffuse interface at equilibrium as illustrated in Fig. 6.<br /> <br /> <br /> [[File:TRR150-Fig-Grid-Resolution.png|850px|thumb|center|Fig. 6: Initial phase distribution with magnified views of the diffuse interface for different grid resolutions employed in numerical simulations.]]<br /> <br /> <br /> Further details can be found in the following publication: <br /> <br /> M. Bagheri, B. Stumpf, I.V. Roisman, C. Tropea, J. Hussong, M. Wörner, H. Marschall, ''Interfacial relaxation – Crucial for phase-field methods to capture low to high energy drop-film impacts'', Int. J. Heat Fluid Flow 94 (2022) 108943, https://doi.org/10.1016/j.ijheatfluidflow.2022.108943<br /> <br /> &lt;br/&gt;<br /> ----<br /> {{ACContribs<br /> |authors=Milad Bagheri, Bastian Stumpf, Ilia V. Roisman, Cameron Tropea, Jeanette Hussong, Martin Wörner, Holger Marschall<br /> |organisation=Technical University of Darmstadt and Karlsruhe Institute of Technology<br /> }}<br /> {{EXPHeader<br /> |area=1<br /> |number=4<br /> }}<br /> <br /> <br /> © copyright ERCOFTAC {{CURRENTYEAR}}</div> Mike https://kbwiki.ercoftac.org/w/index.php?title=EXP_1-4_Experimental_Set_Up&diff=44755 EXP 1-4 Experimental Set Up 2023-08-17T10:01:12Z <p>Mike: </p> <hr /> <div><br /> =Axisymmetric drop impact dynamics on a wall film of the same liquid=<br /> {{EXPHeader<br /> |area=1<br /> |number=4<br /> }}<br /> __NOTOC__<br /> = Experimental Setup=<br /> <br /> The experimental setup shown in Fig. 3 can be divided into three<br /> main units including the drop generator, the impact substrate and the<br /> observation system. <br /> <br /> * The '''drop generator''' is based on a drop on demand method. A micropump transports the liquid from a tank to the cannula. The drop drips off the cannula tip by gravity as soon as the critical mass is reached. A vertical tube reduces the influence of the air flow in the room on the trajectory of the falling drop, so that the point of impact remains reproducible. The impact velocity of the drop is varied by altering the height of the cannula tip relative to the liquid film interface. <br /> <br /> * The '''impact substrate''' is an aluminum block with a recess of 70 mm diameter and 0.6 mm depth. The recess constrains the liquid so that films with a defined film thickness can be placed. The film thickness is measured by a chromatic line Sensor (Precitec CHRocodile CLS) which allows measuring the film thickness on 192 points aligned on a line of 1 mm length, to assure uniform film thickness. <br /> <br /> * The '''observation system''' is described in [[EXP 1-4 Measurement Quantities and Techniques]]. There, also a suitable setup for CFD calculations is given.<br /> <br /> <br /> [[File:TRR150-Fig-Setup.png|400px|thumb|center|Fig. 3: Schematic representation of the experimental setup.]]<br /> <br /> <br /> &lt;br/&gt;<br /> ----<br /> {{ACContribs<br /> |authors=Milad Bagheri, Bastian Stumpf, Ilia V. Roisman, Cameron Tropea, Jeanette Hussong, Martin Wörner, Holger Marschall<br /> |organisation=Technical University of Darmstadt and Karlsruhe Institute of Technology<br /> }}<br /> {{EXPHeader<br /> |area=1<br /> |number=4<br /> }}<br /> <br /> <br /> © copyright ERCOFTAC {{CURRENTYEAR}}</div> Mike https://kbwiki.ercoftac.org/w/index.php?title=EXP_1-4_Description&diff=44754 EXP 1-4 Description 2023-08-17T10:00:56Z <p>Mike: </p> <hr /> <div><br /> =Axisymmetric drop impact dynamics on a wall film of the same liquid=<br /> {{EXPHeader<br /> |area=1<br /> |number=4<br /> }}<br /> __NOTOC__<br /> = Description of Study Test Case =<br /> <br /> A sketch of the general set-up of the experiment and the geometry is shown in Fig. 3 in Section [[EXP 1-4 Experimental Set Up]] while the principal quantities measured are given in Section [[EXP 1-4 Measurement Quantities and Techniques]]. The liquid used in the experiments is silicone oil (density ''&amp;rho;'' = 920 kg/m&lt;sup&gt;3&lt;/sup&gt;, kinematic viscosity ''&amp;nu;'' = 5 &amp;sdot; 10&lt;sup&gt;-6&lt;/sup&gt; m&lt;sup&gt;2&lt;/sup&gt;/s, surface tension ''&amp;sigma;'' = 0.0177 N/m) and the ambient gas is air (density 1.2 kg/m&lt;sup&gt;3&lt;/sup&gt;, kinematic viscosity 1.52 &amp;sdot; 10&lt;sup&gt;-5&lt;/sup&gt; m&lt;sup&gt;2&lt;/sup&gt;/s). The film height ''h'' = 500 μm as well as the drop diameter ''D'' = 1.5 mm are kept fixed, resulting in the dimensionless film thickness ''δ'' = ''h''/''D'' = 0.33. The drop velocity ''U'' is varied from 1 to 3 m/s. Accordingly, the Weber number ''We'' = ''&amp;rho;DU''&lt;sup&gt;2&lt;/sup&gt;/''&amp;sigma;'' is in the range 78 &amp;ndash; 702 while the Reynolds number ''Re = DU/&amp;nu;'' is in the range 300 &amp;ndash; 900, see Table 1. <br /> For each impact velocity a video is provided for download. The meaning of the file names is as follows: S5 = silicon oil with kinematic viscosity 5 mm&lt;sup&gt;2&lt;/sup&gt;/s, D1p5 = drop diameter 1.5 mm , H500 = film height 500 µm. The digit after U denotes the drop impact velocity in m/s, e.g. U3 = 3 m/s. <br /> <br /> <br /> {|class=&quot;wikitable&quot; style=&quot;margin:auto;text-align: center&quot;<br /> |+ Table 1: Investigated drop impact velocities<br /> |-<br /> ! Impact energy !! Impact velocity !! Weber number !! Reynolds number !! Link for video download<br /> |-<br /> | Low || 1 m/s || 78.0 || 300 || [[Media:S5_D1p5_H500_U1.avi|Download S5_D1p5_H500_U1]]<br /> |-<br /> | Moderate || 2 m/s || 311.9 || 600 || [[Media:S5_D1p5_H500_U2.avi|Download S5_D1p5_H500_U2]]<br /> |-<br /> | High || 3 m/s || 701.7 || 900 || [[Media:S5_D1p5_H500_U3.avi|Download S5_D1p5_H500_U3]]<br /> |}<br /> <br /> <br /> &lt;br/&gt;<br /> ----<br /> {{ACContribs<br /> |authors=Milad Bagheri, Bastian Stumpf, Ilia V. Roisman, Cameron Tropea, Jeanette Hussong, Martin Wörner, Holger Marschall<br /> |organisation=Technical University of Darmstadt and Karlsruhe Institute of Technology<br /> }}<br /> {{EXPHeader<br /> |area=1<br /> |number=4<br /> }}<br /> <br /> <br /> © copyright ERCOFTAC {{CURRENTYEAR}}</div> Mike https://kbwiki.ercoftac.org/w/index.php?title=EXP_1-4_Review_of_Studies&diff=44753 EXP 1-4 Review of Studies 2023-08-17T10:00:39Z <p>Mike: </p> <hr /> <div><br /> =Axisymmetric drop impact dynamics on a wall film of the same liquid=<br /> {{EXPHeader<br /> |area=1<br /> |number=4<br /> }}<br /> __NOTOC__<br /> = Review of Experimental Studies and choice of test case =<br /> <br /> Comprehensive reviews on the drop impact onto a solid substrates wetted by a thin film can be found in Yarin (2006), Liang &amp; Mudawar (2016) and Yarin, Roisman &amp; Tropea (2017). <br /> <br /> Experiments on the dynamics of the droplet-wall-film interaction in the event that the entire impact process is rotational symmetrical are lacking so far. Such data are highly relevant for the development of simulation methods, since the numerical effort of axisymmetric computations remains limited compared to 3D calculations and extensive comparative studies can be carried out for validation and methodical developments. The present experiment provides such data and has been especially designed for the validation of CFD methods for numerical simulation of two-phase flows where the gas-liquid interface is well resolved.<br /> <br /> A.L. Yarin, Drop impact dynamics: Splashing, spreading, receding, bouncing... Annu. Rev. Fluid Mech., 38 (2006) 159-192, https://doi.org/10.1146/annurev.fluid.38.050304.092144<br /> <br /> G. Liang, I. Mudawar, Review of mass and momentum interactions during drop impact on a liquid film, Int. J. Heat Mass Transf., 101 (2016) 577-599, https://doi.org/10.1016/j.ijheatmasstransfer.2016.05.062<br /> <br /> A.L. Yarin, I.V. Roisman, C. Tropea, Collision phenomena in liquids and solids, Cambridge University Press, Cambridge, United Kingdom, 2017, https://doi.org/10.1017/9781316556580<br /> <br /> &lt;br/&gt;<br /> ----<br /> {{ACContribs<br /> |authors=Milad Bagheri, Bastian Stumpf, Ilia V. Roisman, Cameron Tropea, Jeanette Hussong, Martin Wörner, Holger Marschall<br /> |organisation=Technical University of Darmstadt and Karlsruhe Institute of Technology<br /> }}<br /> {{EXPHeader<br /> |area=1<br /> |number=4<br /> }}<br /> <br /> <br /> © copyright ERCOFTAC {{CURRENTYEAR}}</div> Mike https://kbwiki.ercoftac.org/w/index.php?title=EXP_1-4_Introduction&diff=44752 EXP 1-4 Introduction 2023-08-17T10:00:26Z <p>Mike: </p> <hr /> <div><br /> =Axisymmetric drop impact dynamics on a wall film of the same liquid=<br /> {{EXPHeader<br /> |area=1<br /> |number=4<br /> }}<br /> __NOTOC__<br /> = Introduction =<br /> <br /> This contribution is based on the publication by Bagheri et al. (see reference below), where the normal impact of a single drop onto a wall film of the same liquid is investigated experimentally and numerically. Droplet impact onto wetted surfaces is of pertinence to many technical applications such as internal combustion engines, automotive exhaust gas after-treatment, icing on plane wings and spray coating technologies to name a few. Immediately after the impact, the droplet expands radially along the surface. If the impact kinetic energy is sufficiently high, an upward growing crown is generated with detachment of secondary droplets. <br /> <br /> For the cases considered here, splashing is absent and the drop-film interaction is axisymmetric. The two-phase flow is laminar and its dynamics is governed by an interplay between inertial, viscous and capillary forces. The formation and expansion of the crown and the associated flow field in both phases are illustrated in Fig. 2 showing results of numerical simulations. Experimental videos of the drop-film interaction are provided for download in Section [[EXP 1-4 Description]]. From these videos, experimental data for the time evolution of the three characteristic dimensions of the crown are extracted, namely the height of the crown and its top and base radius (see Section [[EXP 1-4 Measurement Quantities and Techniques]].). <br /> <br /> <br /> [[File:TRR150-Fig-10-Paper.png|600px|thumb|center|Fig. 2: Snapshots of phase distribution and velocity field from axisymmetric numerical simulations (moderate drop impact velocity 2 m/s).]]<br /> <br /> The present test case is based on the publication<br /> <br /> M. Bagheri, B. Stumpf, I.V. Roisman, C. Tropea, J. Hussong, M. Wörner, H. Marschall, ''Interfacial relaxation – Crucial for phase-field methods to capture low to high energy drop-film impacts'', Int. J. Heat Fluid Flow 94 (2022) 108943, https://doi.org/10.1016/j.ijheatfluidflow.2022.108943<br /> <br /> and the underlying research was funded by the Deutsche Forschungsgemeinschaft (DFG, German Research Foundation) within the '''CRC/TRR 150 Turbulent, chemically reactive, multi-phase flows near walls''', project number 237267381. https://www.trr150.tu-darmstadt.de/der_sonderforschungsbereich/index.en.jsp<br /> <br /> &lt;br/&gt;<br /> ----<br /> {{ACContribs<br /> |authors=Milad Bagheri, Bastian Stumpf, Ilia V. Roisman, Cameron Tropea, Jeanette Hussong, Martin Wörner, Holger Marschall<br /> |organisation=Technical University of Darmstadt and Karlsruhe Institute of Technology<br /> }}<br /> {{EXPHeader<br /> |area=1<br /> |number=4<br /> }}<br /> <br /> <br /> © copyright ERCOFTAC {{CURRENTYEAR}}</div> Mike https://kbwiki.ercoftac.org/w/index.php?title=EXP_1-4&diff=44751 EXP 1-4 2023-08-17T10:00:06Z <p>Mike: </p> <hr /> <div><br /> =Axisymmetric drop impact dynamics on a wall film of the same liquid=<br /> {{EXPHeader<br /> |area=1<br /> |number=4<br /> }}<br /> __NOTOC__<br /> = Abstract =<br /> <br /> The dynamics of the normal impact of a single drop onto a thin wall film of the same liquid is characterized experimentally (using high-speed shadowgraphy) and by numerical simulations (using a diffuse-interface phase-field method). The initial kinetic energy of the drop is sufficiently high to give rise to the formation of a notable crown (corona) but sufficiently low to avoid any disintegration of the crown. Splashing is thus avoided and the entire dynamics of the drop-film interaction is laminar and rotational symmetric. This makes the data set especially useful for advancement and validation of interface-resolving numerical methods for two-phase flows. In addition to videos of the drop-film interaction, time-resolved experimental and numerical data on three characteristic dimensions of the crown (height, base diameter, top diameter) are provided for two different impact velocities. The experimental results are used to develop an extended surface tension model for the phase-field method, which is suitable for highly dynamic two-phase flows. <br /> <br /> <br /> [[File:TRR150-Fig-Comp.png|850px|thumb|center|Fig. 1: Comparison of crown shape (left image) and crown height (right image) between experiment and simulation for moderate impact velocity.]]<br /> <br /> &lt;br/&gt;<br /> ----<br /> {{ACContribs<br /> |authors=Milad Bagheri, Bastian Stumpf, Ilia V. Roisman, Cameron Tropea, Jeanette Hussong, Martin Wörner, Holger Marschall<br /> |organisation=Technical University of Darmstadt and Karlsruhe Institute of Technology<br /> }}<br /> {{EXPHeader<br /> |area=1<br /> |number=4<br /> }}<br /> <br /> <br /> © copyright ERCOFTAC {{CURRENTYEAR}}</div> Mike