Plasma-Based Actuators for Cylinder Wake Vortex Control

Abstract

A number of methods have been developed over the years to affect the wake of a circular cylinder. These include oscillation of the cylinder normal to the direction of flow, rotational oscillation, and blowing and suction through slots. While each of these methods has been found effective for operation at low Reynolds numbers, their low bandwidth, resonance, or form factor make them generally unsuitable for robust operation. As the field of flow control aims to affect flows of Reynolds numbers of technical interest, there is a need for actuators with higher bandwidth and non-resonant behavior for robust mitigation of Karman Vortex Street-induced drag and oscillatory lift. The dielectric barrier discharge (DBD) plasma electrode has been developed as a flow control actuator over the last few years, showing the ability to affect flow behavior in a range of applications. In this effort, the DBD plasma actuator is applied to a circular cylinder at a Reynolds number of 7400. Hot film measurements show that vortex shedding frequency can be driven to the actuator forcing frequency, exhibiting lock-in behavior similar to that previously shown with the other forcing methods. Preliminary data indicates that plasma actuators are effective in controlling vortex shedding frequency and in achieving spanwise coherent shedding. They also can alter the vortex shedding frequency within forcing amplitude/frequency bands similar to that for the above methods at lower Reynolds number. Flow visualization shows the actuators have significant authority in affecting flow separation and wake behavior.