Flow Separation Control Using Unsteady Sawtooth Plasma Actuator

Flow separation control is an important issue in the field of fluid engineering.Our main research aims to study the influence of unsteady dielectric material discharge?DBD?plasma actuator to the flow separation of NACA0015 airfoil,and investigate the mechanism responsible for flow reattachment.This paper firstly characterize the power,jet velocity and flow visualization of the unsteady plasma actuator setting on the plate in free-stream flow,and then investigate the aerodynamic effect with the unsteady plasma actuator applied on the airfoil in wind tunnel,finally characterize the mechanism of flow control under unsteady plasma actuator control using PIV.We found that the unsteady plasma actuator power consumption not vary with the pulse frequency,but fit linear Relationship with duty cycle.And the average induced velocity also isn't changed by the variation of pulse frequency,and increase with higher duty cycle.We investigate that the unsteady sawtooth plasma actuator can induce a pair of vortex form the trough Region,and the vortex only appear when the pulse switch on,but disappear rapidly in the power off Region.The investigation of aerodynamic effect on the airfoil in wind tunnel shows that at?=16°and U_?=6m/s,the unsteady sawtooth DBD plasma actuator can effectively control the flow separation,and significantly increase the lift coefficient of the airfoil.The best control effect appears at F⁺=0.6,DC=5%,now the sawtooth plasma actuator led to a delay of stall?by 3°and the C_Lmaxmax was increased by about 27.5%,whereas the steady sawtooth plasma actuator manages a delay of stall angle by 5°,and the C_Lmaxmax was only increase by 9%.The unsteady sawtooth plasma actuator can not only increase separation control effect,but can save 95%of power consumption.The PIV results illustrated that under unsteady actuation control,the sawtooth plasma actuator will produce impulse discharge which will produce significant disturbance and interact with the separated shear layer and promote momentum transfer from the external flow to the boundary layer,thus forcing the flow reattachment to the airfoil surface.