Effect of surface heating on shock wave modification by a plasma actuator in a rarefied supersonic flow over a flat plate

Abstract

This paper describes experimental and numerical investigations focused on the shock wave modification induced by a plasma actuator. The studied model is a flat plate placed in a rarefied Mach 2 air flow. The plasma actuator is composed of two metallic electrodes set on the upper surface of the model. A negative dc potential is applied to the upstream electrode in order to generate an abnormal glow discharge and, thus, to create a weakly ionized plasma around the model. ICCD images of the flow allow the shock wave to be detected and its angle to be estimated. When the discharge is ignited, the shock wave angle increases with the discharge current. In addition, an IR camera is used to measure the increase in the surface temperature. The longitudinal distributions of the surface temperature are used as boundary conditions in the numerical simulations of the surface heating induced by the plasma actuator. This type of thermal effect is reproduced experimentally with a heating element designed to this purpose. For the same surface heating, experimental results show that the shock wave angle is higher in the case of the plasma actuator: surface heating is responsible for roughly 50% of the shock wave angle modification. The numerical simulations are used to studied the aerodynamic forces modifications in the case of the surface heating. The results are extrapolated to the plasma actuator in order to estimate the variations in the drag and lift coefficients.