The aim of this study is to introduce streamwise vortex pairs generated by plasma actuators into separated shear layer from circular cylinder. The electrodes of the plasma actuator placed on the surface of the circular cylinder were arranged in the spanwise direction. Induced jets by the actuators interacted each other and produced streamwise vortex pairs. Flow visualizations in still fluid and in the wake region of the cylinder were performed by a high speed camera and PIV analysis. Vortex structure in the wake behind the circular cylinder was measured by X-type hot-wire measurement. It was found that the streamwise vortex pairs affected the vortical structure in shear layer from circular cylinder.
