Flow Separation Control with a Plasma Actuator Over a Metallic NACA 4418

Abstract

The flow control over an airfoil was experimentally investigated with a Dielectric Barrier Discharge (DBD) plasma actuator. A NACA 4418 airfoil was used and the fact that it is metallic is the main difference with the numerous articles about plasma actuators over airfoils. Metallic airfoils are normally avoided to reduce risk of arcing and electromagnetic interferences. The plasma actuator was located at x/c = 0.1 measured from the leading edge. Through the Schlieren visualization, the characteristics of the actuator in a quiescent ambient was observed, showing a double wall jet due to the interaction of the plasma actuator and the metallic airfoil used as substrate. One of them is a co-flow wall jet and the other one is a counter-flow wall jet. Time-averaged Particle Image Velocimetry (PIV) images were used to examine the flow for different angles of attack at Rec = 40.000 and Rec = 200.000 when plasma is on and off. Velocity maps show that the plasma actuation delays the separation for both low and moderate Reynolds numbers. The turbulent kinetic energy (TKE) and Reynolds stress values are reduced when plasma can control the flow, however plasma actuator increases these values when it does not avoid the separation. The velocity magnitude profiles show the influence of the co-flow wall jet near exposed-electrode but the counter-flow is not observed. A reduction of the wake with plasma actuation is also seen. The results confirm the authority of plasma actuators to control the flow separation over a metallic airfoil. The effectiveness and the global performance in applications such as wind turbines or UAVs at moderate Reynolds number, where metallic airfoils are used, is expected to be improved avoiding the separation with plasma actuators.