Simulation of acoustic oscillatory flows around a curvature controlled by a plasma actuator

Abstract

In this study, simulations based on the three-dimensional compressible Navier–Stokes equations were conducted to clarify a control method with a plasma actuator to reduce the acoustic power loss in the oscillatory flow under acoustic excitation (acoustic oscillatory flow) in a curved duct. The acoustic power loss for the curved duct exceeds that for the straight duct, particularly at a high acoustic Reynolds number based on the amplitude of the velocity fluctuations in the duct. Flow control by a plasma actuator, which was installed near the curvature in the straight section, was applied to suppress the periodically occurring flow separation around the curvature, which leads to energy loss in the baseline flow. The plasma actuator was intermittently driven at the same frequency as the acoustic oscillatory flow. It was thus demonstrated in the present numerical simulations that the acoustic power loss around the curvature was reduced by the flow control with the plasma actuator. Furthermore, efficient control conditions for the number of plasma actuators and the driving voltage are discussed considering the power consumption of the plasma actuator, although the power efficiency of the control needs to be improved for actual application. Moreover, the relatively effective intermittent control conditions of the phase and duty ratio for the reduction of acoustic power loss are presented with the predicted flow fields around the curvature.