Wake behind circular cylinder excited by spanwise periodic disturbances using DBD plasma actuator array

We experimentally investigated flow control of the wake behind a circular cylinder excited by temporal periodic disturbances with spanwise phase variations using DBD plasma actuator array, motivated by reducing drag forces by suppressing development of large scale vortices. DBD plasma actuator were segmented in the spanwise direction, and phase differences were given to adjacent electrodes. This experiment was conducted at Re≃8000 and the wake was visualized by PIV. Compared to without forcing, when the phase difference is 180° and non-dimensional forcing frequency is higher than approximately 1.0, small vortices induced by periodic disturbance emerged in the free shear layer. Then, wavy vortex structures along spanwise direction caused by phase differences were observed in the free shear layer by stereo PIV and resulting in reduction of drag forces.