Experimental comparison between the effect of electrical discharge and the effect of surface heating on Mach 2 rarefied airflow over a flat plate

Abstract

This study describes the experimental investigation of the effect of a negative DC glow discharge on a Mach 2 rarefied airflow around a flat plate. More precisely, we will show a comparison between two experiments. In the first one we will observe the effect of discharge by Pitot probe measurement. This discharge is created by applying negative DC potential difference between two electrodes flush mounted on the surface of a quartz flat plate placed in Mach 2 rarefied airflow. The electrodes are arranged in the spanwise direction. In the second experiment, electrodes are removed and replaced with a surface heater. The pressure profiles obtained by a glass Pitot tube are presented, and a comparison between the plasma effect and the surface heater effect is made, for the same surface temperature and in thermal equilibrium, with the aim of identifying the origin of the observed effect. For both experiments, surface heating causes a decrease in the boundary layer stagnation pressure, while increasing the boundary layer thickness, with the effects becoming larger for higher mean surface temperature. The effects due to the plasma actuator seem to be larger over the active electrode.