Nonequilibrium Radio Frequency Discharge Plasma Effect on Conical Shock Wave: M = 2.5 Flow

Abstract

An experimental study of shock modi cation in an M = 2:5 supersonic ow of nonequilibrium plasma over a cone is discussed. The experiments are conducted in a nonequilibrium plasma supersonic wind tunnel. Recent experiments at the Ohio State University using a supersonic plasma ow over a quasi-two-dimensional wedge showed that an oblique shock can be considerably weakened by a transverse rf discharge plasma. The previously observed shock weakening, however, has been found consistent with a temperature rise in the boundary layers heated by the discharge. In the present study, the boundary-layereffects on the shock wave are reduced by placing an entire cone model into a supersonic inviscid core ow. The electron density in the supersonic plasma ow in the test section is measured using microwave attenuation. The ionization fraction in the discharge is in the same range as in the previous plasma shock experiments, up to n e /N = (1.2-3.0) £ £ 10 ¡7 . The results do not show any detectable shock weakening by the plasma. This strongly suggests that the previously observed shock weakening and dispersion in nonequilibrium plasmas are entirely due to thermal effects.

Streamer Self-Focusing in External Longitudinal Magnetic Field

“…To this end, supersonic discharges for pumping such lasers have been reported in molecular flows using DC discharges [7−9], electron beam stabilization techniques [10], and a 13.56-MHz RF discharge [11]. Recent progress has been made at the Ohio State University also using a 13.56-MHz RF source to drive a volume-filling discharge in Mach 2.5 airflow [12]. Pulsed ionization schemes in conjunction with DC discharges have also been implemented successfully in subsonic flows to reduce arcing in CO 2 lasers.…”

Development and use of localized arc filament plasma actuators for high-speed flow control

“…Previous work on thermal flow control includes energy addition using bulk heating of the flow by diffuse nonequilibrium plasmas [16][17][18][19][20][21], or localized heating by a plasma torch or by a pulsed laser breakdown [22][23][24][25][26][27]. Bulk heating of the flow to weaken the shock in a high-speed flow requires an extremely high plasma power budget (comparable with the flow enthalpy).…”

Experimental investigation of the properties of a glow discharge used as plasma actuator applied to rarefied supersonic flow control around a flat plate

“…It can be observed that for a large part of the applied voltage values experimentally tested, the ionization degree of the plasma upstream the flat plate ranges between 10 -4 and 10 -3 . This range is much higher than the one estimated by [47] (1.2-3.0×10 -7 ), for which the shock wave modifications were attributed to only thermal effects.…”