Flow Control Channel behind a Backward-Facing Step in a Duct

Abstract

Flow control over a backward-facing step (BFS) by continuous suction/blowing is numerically investigated. This study examines the influence of blowing/suction rate, and slot size on the detachment process. Fluid flow is assumed turbulent, incompressible, 2D and steady in average. The governing equations are discretised by the finite volume method based on the k-ε RNG one point closure turbulence model. The investigations were performed for a Reynolds number of 3.5 104 with respect to the step height (h). Several blowing/suction rates are checked (-0.035 < Cq < +0.035) for four slot size cases namely (a = 0.95 mm, 2.25 mm, 3 mm and 5 mm). All results indicate that suction/blowing shortens the reattachment length and reduces the turbulence energy. The detailed flow structure suggests a way of shortening of the recirculation length with increasing the blowing/suction rate. Through different flow conditions, two correlations for reattachment length related to blowing or suction rate are proposed. The smallest slot size produces greatest turbulence kinetic energy and maximum friction all considered suction/blowing rates.