Turbulent separated inert and reactive flows over a triangular bluff body

Application Challenge AC2-12 © copyright ERCOFTAC 2019

Evaluation

Comparison of test data and CFD

Introduction

All simulated cases are listed in Table 6, where the following abbreviations are used: Code – the computational code: Ansys Fluent (AF) or OpenFOAM (OF), M – mesh: according to Section 4.2, N – convective schemes: the second-order upwind (SOU), the normalized variable diagram (NVD) (γ ), the total variation diminishing (TVD), CF – flow conditions: according to Table 1, TR – the approach for solution of the Navier-Stokes equations, (U)RANS , SAS or LES, TM – turbulence model: k-ε (SKE), k-ω SST (SST), k-equation eddy-viscosity sub-grid scale model (TKE), Smagorinsky (SMAG), TCM – turbulence-chemistry interaction model: Eddy Dissipation Concept (EDC), Turbulent Flame Closure (TFC), CH – chemistry mechanism: according to Section 2.5.2, R – radiation sub-model: P1 or none, Sct – turbulence Schmidt number, Prt – turbulence Prandtl number, Two and Twc – temperature boundary conditions for the obstacle and channel walls, respectively: zero-gradient (zg), isothermal (Tisoth = 300 K and Tisoth = 600 K for cases C1 and C2, respectively) or conjugate fluid-solid heat transfer (CHT). For a quantitative validation of the present SAS and LES simulations, the averages have been obtained from the computational results by sampling over 40 vortex shedding periods (Nvs ) for the SAS non-reactive solution and three flow-through times for the combustion SAS and LES. The flow-through time was defined as the ratio between the axial length of the computational domain to the jet bulk velocity.

Table 6: Run matrix for the Volvo test rig.

Inert calculations (SAS,URANS)

Figure 9 shows the measured and predicted mean stream-wise velocity and its fluctuation as well as the normalized turbulence kinetic energy along the central-line behind the obstacle (for case C0). For the sake of completeness, besides the LDA data by Sjunnesson et al. [2], the LDV data by Sanquer et al. [10], who had investigated inert bluff-body wakes as well as premixed bluff-body combustion, were added to the plot. The experimental data by Sanquer et al. [10] have been obtained for the Reynolds number, Re ≈ 6×10³, based on the bluff body height (case i3). Another important parameter in this experiment, the blockage ratio (the ratio between bluff-body to channel heights) was 0.33 as in the Volvo test rig.

Contributed by: D.A. Lysenko and M. Donskov — 3DMSimtek AS, Sandnes, Norway