Aerodynamic flow control using paraelectric and peristaltic acceleration of a one atmosphere uniform glow discharge plasma

Abstract

Summary form only given. Plasma actuators based on the One Atmosphere Uniform Glow Discharge Plasma (OAUGDP/spl trade/) can be used to accelerate and reattach flows, increase the stall angle of airfoils, and modify the aerodynamic boundary layer of aircraft at the relatively low power cost of 5 to ten watts per linear foot of actuator. The characteristics and performance of OAUGD plasma actuators have been measured in the 7/spl times/11 Low Speed Wind Tunnel located at the NASA Langley Research Center. This wind tunnel was used to conduct drag measurements, smoke visualization studies, boundary layer velocity profile measurements, and flow attachment tests. This paper discusses two EHD (electrohydrodynamic) processes that utilize RF displacement currents to produce the body forces that accelerate the plasma: paraelectric and peristaltic (traveling wave) flow acceleration. Paraelectric flow acceleration results when the applied electric field acts on the net charge density of the plasma to provide a body force capable of accelerating the neutral gas to velocities up to 10 m/sec. During this process, the plasma moves paraelectrically towards increasing electric field gradients, and drags the neutral gas along with it as the result of frequent ion-neutral collisions. Peristaltic flow acceleration uses a polyphase power supply to energize successive OAUGDP/spl trade/ plasma actuators at progressive voltage phase angles. The resulting horizontal electric field of the traveling electrostatic wave produces a body force that accelerates the plasma, analogous to the apparent motion of light in a phased array of bulbs on a theatre marquee. A OAUGDP/spl trade/ plasma actuator intended for aerodynamic applications consists of electrodes flush mounted on either side of a dielectric panel. The panels are energized by a RF power supply that characteristically operates at voltages between 0 and 10 kV, and frequencies between 0.5 kHz and 8 kHz. During our plasma actuator development program, many electrode geometries were designed and investigated to obtain optimum operating conditions. Parametric dependencies from the flow visualization and velocity profile tests are presented for a wide range of operating conditions, and the need to establish an optimum operating condition is discussed.