Optimization of the Aerodynamic Plasma Actuator as an Electrohydrodynamic (EHD) Electrical Device

Abstract

Electrohydrodynamic plasma actuators have proven effective for flow attachment in internal and external aerodynamics, and for modification of the lift, drag, and stall angle of airfoils. The performance of plasma actuators has been studied with such classical aerodynamic tools as wind tunnels, drag balances, Pitot tubes, smoke flow visualization, and fluid dynamic modeling programs. However, the physical processes and power flows that occur in plasma actuators, before the plasma ions transfer their momentum to the neutral background gas, are those of an electrical device. Optimization of such actuators needs to include the methods of electrical engineering and plasma physics, including classical electrical discharge physics. To implement a program of optimization, we have conceptually divided the power flow through a plasma actuator into the following four sinks: 1.) Reactive power losses due to inadequate impedance matching of the power supply to the actuator; 2.) Dielectric heating of the actuator insulating materials; 3.) Power required to maintain the atmospheric pressure plasma; and 4.) Power coupled to the neutral gas flow by ion-neutral collisions. These four power flows can be, and usually are, of comparable magnitude. In this paper, we review our progress in understanding and minimizing the first three power flows, and maximizing the fourth by adjustment of the actuator geometry and materials, as well as such plasma parameters as the RF frequency and RMS voltage.