UFR 4-16 Test Case: Difference between revisions
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|'''Figure 3:'''Geometry of the 3-D diffuser 1 considered (not to scale), [[UFR_4-16_References#7|Cherry ''et al.'' (2008)]]; see also Jakirlić ''et al.'' (2010a) | |'''Figure 3:''' Geometry of the 3-D diffuser 1 considered (not to scale), [[UFR_4-16_References#7|Cherry ''et al.'' (2008)]]; see also [[UFR_4-16_References#14|Jakirlić ''et al.'' (2010a)]] | ||
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Revision as of 11:01, 30 July 2012
Flow in a 3D diffuser
Confined flows
Underlying Flow Regime 4-16
Test Case Study
Brief description of the test case studied
The diffuser shapes, dimensions and the coordinate system are shown in Figs. 3 and 4. Both diffuser configurations considered have the same fully- developed flow at channel inlet but slightly different expansion geometries: the upper-wall expansion angle is reduced from 11.3o (Diffuser 1) to 9o (Diffuser 2) and the side-wall expansion angle is increased from 2.56o (Diffuser 1) to 4o (Diffuser2). The flow in the inlet duct (height h=1 cm, width B=3.33 cm) corresponds to fully-developed turbulent channel flow (enabled experimentally by a development channel being 62.9 channel heights long). The L=15h long diffuser section is followed by a straight outlet part (12.5h long). Downstream of this the flow goes through a 10h long contraction into a 1 inch diameter tube. The curvature radius at the walls transitioning between diffuser and the straight duct parts are 6 cm (Diffuser 1) and 2.8 cm (Diffuser 2). The bulk velocity in the inflow duct is [pic] in the x-direction resulting in the Reynolds number based on the inlet channel height of 10000. The origin of the coordinates (y=0, z=0) coincides with the intersection of the two non-expanding walls at the beginning of the diffuser's expansion (x=0). The working fluid is water (?=1000 kg/m3 and ?=0.001 Pas).
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| Figure 3: Geometry of the 3-D diffuser 1 considered (not to scale), Cherry et al. (2008); see also Jakirlić et al. (2010a) |
Test Case Experiments
Provide a brief description of the test facility, together with the measurement techniques used. Indicate what quantities were measured and where.
Discuss the quality of the data and the accuracy of the measurements. It is recognized that the depth and extent of this discussion is dependent upon the amount and quality of information provided in the source documents. However, it should seek to address:
- How close is the flow to the target/design flow (e.g. if the flow is supposed to be two-dimensional, how well is this condition satisfied)?
- Estimation of the accuracy of measured quantities arising from given measurement technique
- Checks on global conservation of physically conserved quantities, momentum, energy etc.
- Consistency in the measurements of different quantities.
Discuss how well conditions at boundaries of the flow such as inflow, outflow, walls, far fields, free surface are provided or could be reasonably estimated in order to facilitate CFD calculations
CFD Methods
Provide an overview of the methods used to analyze the test case. This should describe the codes employed together with the turbulence/physical models examined; the models need not be described in detail if good references are available but the treatment used at the walls should explained. Comment on how well the boundary conditions used replicate the conditions in the test rig, e.g. inflow conditions based on measured data at the rig measurement station or reconstructed based on well-defined estimates and assumptions.
Discuss the quality and accuracy of the CFD calculations. As before, it is recognized that the depth and extent of this discussion is dependent upon the amount and quality of information provided in the source documents. However the following points should be addressed:
- What numerical procedures were used (discretisation scheme and solver)?
- What grid resolution was used? Were grid sensitivity studies carried out?
- Did any of the analyses check or demonstrate numerical accuracy?
- Were sensitivity tests carried out to explore the effect of uncertainties in boundary conditions?
- If separate calculations of the assessment parameters using the same physical model have been performed and reported, do they agree with one another?
Contributed by: Suad Jakirlić, Gisa John-Puthenveettil — Technische Universität Darmstadt
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