Mass transfer control of a backward-facing step flow by local forcing-effect of Reynolds number

Abstract

The control of fluid mechanics and mass transfer in separated and reattaching flow over a backward-facing step by a local forcing, is studied using Large Eddy Simulation (LES). To control the flow, the local forcing is realized by a sinusoidal oscillating jet at the step edge. The Reynolds number is varied in the range 10000 ? Re ? 50000 and the Schmidt number is fixed at 1. The found results show that the flow structure is modified and the local mass transfer is enhanced by the applied forcing. The observed changes depend on the Reynolds number and vary with the frequency and amplitude of the local forcing. For the all Reynolds numbers, the largest recirculation zone size reduction is obtained at the optimum forcing frequency St = 0.25. At this frequency the local mass transfer enhancement attains the maximum.