Large-eddy Simulation of Flow over a Backward Facing Step: Assessment of Inflow Boundary Conditions, Eddy Viscosity Models, and Wall Functions

Abstract

Large-eddy simulation (LES) of turbulent flow over a backward facing step is studied to test the influence of grid resolution, inlet turbulence, wall boundary treatments, and eddy viscosity models. The computational results are validated with experimental data. A grid resolution with 10 cells spanning the step height adequately models the flow, although a doubling of resolution results in the realization of smaller scale kinematic features. The inlet turbulence conditions are determined to be the most significant contributor to downstream flow evolution. Reattachment length is found to be strongly dependent on the magnitude of the inlet root-mean-square velocity. The choice of eddy viscosity model is found to have negligible influence, while the no-slip condition and an LES log-law-based wall function performed similarly for the given flow.