Visualization of vortex ring structure in a synthetic jet

Abstract

A synthetic jet device is a useful tool for active flow control. The vortex ring released from the synthetic jet traverses boundary layer at self-induced velocity and gives momentum in the flow. Synthetic jet actuators require low operating power, however, they can give zero-net-mass-flux and the device can compact. Therefore, a synthetic jet is expected as a new method of boundary layer control. For the synthetic jet, the effect of the orifice depth on the vortex ring behavior has not been completely clarified yet. In this paper vortex ring structure was visualized that was released in cross flow or into quiescent flow for two types of orifice depth and the difference of their structures were compared. The breakdown of the vortex ring in quiescent flow was affected by the orifice depth. The small vortex structures were observed around the collapsed ring. Orifice depth could change the rolling up of the rings and the momentum in the cross flow.