Flow Control over a Two-Element Airfoil Using a Dielectric-Barrier-Discharge Plasma Actuator

Flow control over a two-element airfoil using a symmetrical dielectric-barrier-discharge plasma actuator is studied at the Reynolds number of 1.1x105. The results demonstrated that the lift-drag ratio can be increased by about 21.8% without drag penalty after plasma actuation. Meanwhile, the time-averaged flowfield indicated that the separation region area around the flap is reduced by the plasma actuator. Moreover, the leading-edge stagnation point deflects toward the lower surface of the airfoil, which is similar to the effect of increasing the angle of attack and leads to the increment of the lift. In addition, the controlling mechanisms of the plasma actuator are uncovered based on the instantaneous flowfield results. It is of great importance that two flow structures produced by the interaction between the plasma actuator and the separated shear layer at different times play an important role in suppressing the separation flow by promoting the mixing between the main flow and the flow near the wall surface, and transferring the momentum from the leading edge of the flap to the trailing edge of the flap. The different characteristics of the separated shear layer at different times is the main reason for the generation of different flow structures of the plasma actuator.