Electric discharge in the presence of supersonic shocks

A cone-shaped shock generator is placed in a Mach 2.5 flow to generate a conic shock attached to its tip. The tip and the body of the model are also designed as the cathode and anode, which are separated by a conical-shaped ceramic insulator providing a 5-mm gap for on-board gaseous discharge to produce plasma around the tip. The interaction of 60 Hz pulsed discharge with this shock wave is studied by means of the spatial distribution and temporal evolution of discharge-induced airglow images. As shown, when the flow becomes unstable during the discharge, signified by the sudden appearance of additional diamond shock in the flow, the discharge mode also starts to oscillate between the constricted arc and diffused arc, manifesting relaxation instability. (C) 2003 Elsevier Science B.V. All rights reserved.