Turbulence modeling using Z-F, RSM, LES and WMLES for flow analysis in Z-Shape ducts

Abstract

Turbulent flow in Z-shape duct configuration is investigated and analyzed using Reynolds Stress Model (RSM), Large Eddy Simulation (LES), ζ-f Model, and Wall-Modeled Large Eddy Simulation (WMLES). The results are validated and compared to experimental data. Both RSM and ζ-f models are based on steady-state RANS solutions, while LES and WMLES models account for temporal variations transient behavior of the flow turbulence. The focus was on regions where RSM has over or under predicted the flow and regions where there are flow separations and high turbulence. LES simulation results have shown under-prediction and over-prediction in the flow separation and re-attachment regions. It is found that the turbulent kinetic energy production in ζ equation is much easier to reproduce accurately than other models. Both mean velocity gradient and local turbulent stress terms are also much easier to resolve properly. The current research has found that ζ-f model not only takes less time to complete the simulation but also the mean flow velocity profile results are in better agreement with experimental data than RSM model despite both are coupled steady-state RANS. ζ-f model numerically resolved both the flow separation and re-attachment regions better than RSM model. WMLES model is employed to investigate the SGS model impact on the small eddies dissipated from the large eddies. Such WMLES model produces much better results than the LES model, however the SGS viscosity damps the energy of the flow.