FLOW CONTROL OVER A CIRCULAR CYLINDER USING PLASMA ACTUATORS1)

Abstract

In order to develop a novel technology of Moving Surface Boundary Layer Control (MSBLC) and promote efficiency of flow control technology, flow control over a circular cylinder using two Dielectric Barrier Discharge (DBD) symmetrical plasma actuators was investigated by PIV technology, force measurements and hot wire. The circular cylinder which had a diameter of 50 mm and a spanwise length of 480 mm was placed on the support sting. Here, two symmetrical DBD plasma actuators were mounted at the top and bottom of the circular cylinder respectively. The testing model which was made of aluminum was adopted as the covered electrode and was wrapped by the KAPTON film. The exposed electrodes were copper foil tape which was 2 mm wide and 0.02 mm in thickness. Firstly, time-resolved PIV results in still air indicated that a pair of the starting vortexes which were rotating in the opposite direction was induced as the symmetrical plasma actuator was just started to work. The starting vortexes rolled up and moved away from the wall with time. Then, a bi-directional wall jet on both sides of the exposed electrode was formed by the symmetrical plasma actuator. Due to Coanda Effect, the induced jet moved along the surface of circular cylinder. Secondly, the force and hot wire measurement results under incoming flow suggested that vortex shedding from the circular cylinder can be suppressed significantly by the symmetrical plasma actuators and the drag coefficient was decreased by 21.8％ at the wind speed of 10 m/s. Besides, it can be found that a steady vortex can be formed on the surface of cylinder thanks to the interaction effect between the incoming flow and the induced flow filed by plasma actuator. The induced vortex can transfer high momentum from main flow to the near-wall fluid by rotating and moving, enabling the boundary layer to withstand the adverse pressure gradient and prevent the separation around the circular cylinder and acting as the virtual MSBLC. Compared to the traditional MSBLC, the novel technology of MSBLC which is based on plasma actuator without sophisticated and cumbersome devices cannot bring extra drag and has vast application prospect.