Comparative study of co-flow and counter blowing DBD plasma actuators for separated flow over an airfoil

A comparative study of co-flow and counter-blowing dielectric barrier discharge plasma actuator for separation control is conducted. These actuators are applied with normal mode and burst mode, where normal mode represents the actuation with continuous alternative current (AC) input and burst mode represents the actuation with the AC input switched on and off periodically. They are used for controlling the separated flow around NACA0015 airfoil at low Reynolds number Re_c = 6.3 × 10⁴. Pressure measurement and particle image velocimetry are conducted. In this study, four cases are conducted changing blowing direction, co-flow or counter-blowing, and actuation mode, normal or burst. Comparison among four cases shows that the dominant factor for suppressing separation with burst actuation is promoting transition, regardless of blowing direction. It also shows that the dominant factor of co-flow normal actuation is direct momentum addition. Counter-blowing normal actuation cannot suppress separation with any input voltage. Focusing on the minimum input voltage for suppressing separation, effectiveness for each attached case is compared and it is revealed that burst actuation more or less includes the effect of direct momentum addition.