The Instantaneous Structure of a Turbulent Flow over a Back-Ward-Facing Step

Abstract

The turbulent separating and reattaching flow over a rearward-facing step is investigated using the large eddy simulation (LES) technique. The step flow was chosen as the focus of the investigations because it serves as a prototype for turbulent recirculating flows often occuring in engineering applications. Simulations on coarse and refined (x, y, z) grids of (160 × 32 × 32) and (320 × 64 × 48) nodes, respectively, were performed. The results reveal the detailed flow structure of the separating shear layer, the reattachment zone and the recirculation region. Examination of the instantaneous flow field and comparison with mean values show large departures from the mean in all three regions. Awareness of the instantaneous flow field structure is shown to be instrumental to having a complete understanding of the unsteady turbulent flow.