Plasma Volumetric Effects on the Force Production of a Plasma Actuator

Dielectric barrier discharge plasma actuators are examined experimentally and computationally. Experimental temporal force measurements show that the plasma actuator produces two positive (accelerating) forces per ac cycle. While the plasma is ignited, the actuator experiences an accelerating force, and, when the plasma is extinguished, a decelerating force appears. This occurs twice during each ac bias cycle. In addition, while the accelerating force is approximately equal in magnitude and direction during each half of the ac cycle, the decelerating force is not. Navier-Stokes simulations of the neutral air flow with a prescribed plasma force reveal that the variation in the decelerating actuator force is consistent with structural changes in the plasma itself. These plasma structural changes alter the volume over which the plasma force is imparted to the air and, in turn, change the amount of drag incurred by the wall jet created by the plasma. During each actuator bias cycle, 70-90% of the momentum supplied by the plasma actuator is destroyed by drag with the wall immediately after the plasma extinguishes.