Numerical simulation for control effect of backward-facing step flow by a plasma actuator with burst modulation

Abstract

The backward-facing step channel flow in which the Reynolds number is 1080 is calculated to investigate the control effect by a DBD plasma actuator which is activated with continuous drive or burst modulation. The plasma actuator is located on the edge of the backward-facing step. The conditions for the actuator are 3, 5, 8, and 10 m/s of the surface velocity and 50, 100, 150, and 200 Hz of the burst frequency. When the actuator is activated with the continuous drive, the more the reattachment point moves upstream, the more the induced flow by the actuator is strong. When the burst modulation for the actuator is used, the smaller burst frequency makes the reattachment point move further upstream generally. The reattachment point could travel upstream if a huge vortex has a negative vorticity is generated by merging two vortices near the step. This is because that the huge vortex flows downward with the mainstream flow, on the other hands, if this combining two vortices is not appeared, the reattachment point is little changed. In addition, the mechanism for moving upstream for the reattachment point by the actuator is different for using the continuous drive or the burst modulation. In the continuous drive, the strong enough induced flow by the actuator becomes unstable near the step and flows downward with the mainstream flow, but in the burst modulation, the merged vortex from the mainstream flow appears near the step because a certain period by the burst modulation is introduced in the mainstream flow.