Active control of flow over a rounded ramp by means of single and double adjacent rectangular synthetic jet actuators

Abstract

Active control of flow over a rounded ramp with Re=13,700 was studied numerically by using rectangular synthetic jet actuators. Wall-resolved large eddy simulation was utilized to accurately predict the separation and reattachment of the flow. The solution of uncontrolled case as well as controlled by a single synthetic jet in quiescent conditions were validated against available numerical or experimental data. To investigate active flow control, five actuated cases were considered: a single synthetic jet (SS), double synthetic jets with opposite-phase actuation (DS opposite-phase), double synthetic jets with in-phase actuation (DS in-phase), a wide synthetic jet (WSS) with the same momentum coefficient of the DS in-phase but with twice the opening width, and a high momentum single synthetic jet (HSS) similar to SS but with twice the momentum coefficient of DS in-phase. The aim was to compare the flow control efficiency of these cases and identify the most effective configuration. The DS opposite-phase case was identified in previous studies as being able to keep the expelled fluid inside the near-wall region. We found that among the first three cases, the DS in-phase was the most effective in reducing the length of the separated region. In order to illuminate the flow control mechanisms of each case, phase-averaged streamlines of the flow were generated. Also, a passive scalar variable was introduced into the flow to allow for tracking the expelled fluid from the synthetic jets. This passive scalar was used to evaluate and compare the flow control mechanisms in the cases of WSS and HSS. We found that HSS was the most efficient mechanism among the five configurations studied.