Wall Modeled Large Eddy Simulation of Flow over a Backward Facing Step with Synthetic Inlet Turbulence

Abstract

Application of Large Eddy Simulations (LES) to complex high Reynolds number problems has been limited by the computational cost. This paper uses wall layer modeling to mitigate near wall grid resolution requirements and the specification of inlet turbulence to reduce the cost of LES simulations. The wall model uses the two layer approach which is generalized for complex geometries and the synthetic eddy method (SEM) for the generation of inlet boundary conditions. Three different problems are considered, fully developed turbulent channel flow up to a Reynolds number of 2x10 6 , developing channel flow, and flow over a backward facing step at Re=40,000. Predictions with wall modeled LES are compared with available DNS and experimental data. Good agreement of the predicted mean flow velocity field and turbulent statistics with data indicates that the formulated wall modeled LES and the synthetic eddy method can be used effectively to predict high Reynolds number separated flows at a cost at least an order of magnitude less than wall resolved LES.