Numerical simulation of flow separation over a backward-facing step with high Reynolds number

Large eddy simulation (LES) explicitly calculates the large-scale vortex field and parameterizes the small-scale vortices. In this study, LES and κ-ε models were developed for a specific geometrical configuration of backward-facing step (BFS). The simulation results were validated with particle image velocimetry (PIV) measurements and direct numerical simulation (DNS). This LES simulation was carried out with a Reynolds number of 9000 in a pressurized water tunnel with an expansion ratio of 2.00. The results indicate that the LES model can reveal large-scale vortex motion although with a larger grid-cell size. However, the LES model tends to overestimate the top wall separation and the Reynolds stress components for the BFS flow simulation without a sufficiently fine grid. Overall, LES is a potential tool for simulating separated flow controlled by large-scale vortices.