Control reattachment of backward-facing step flow using a row of mini-jets in recirculation bubble

Abstract

In this experimental study, we introduce an open-loop control method for shortening the reattachment length in a backward-facing step flow using a row of pulsatile min-jets in the recirculation bubble. The mini-jet perturbations are imposed in two ways, i.e., in-phase perturbation and traveling-wave perturbation. Both types of perturbations are found to shorten the reattachment length, while the former is more effective and gives comparable extent of the length reduction as the mini-jets imposed at the step separation point. The change in the flow field by the perturbations is unraveled on embedded coherent flow structures.