Mach 3 Shock Wave Unsteadiness AlleviationUsing a Negative Corona Discharge

Abstract

This paper reports experimental data obtained in ONERA M = 3 R1Ch blow-down wind tunnel. A truncated conical body with a central spike mounted on the truncated face is tested in a M = 3 airflow. Several runs have been performed, with a freestream unit Reynolds varying in the range Reu 2 [0.9 10 7 m 1 ; 2.1 10 7 m 1 ]. Depending on the spike length LS, the flow around the body is steady or unsteady. Following Kuo, 1 the model is also a pair of electrodes and is supplied with AC or DC power. Thus on-board discharges can be generated. Although different discharge regimes have been obtained on steady or unsteady flowfield, we simply report here the effect of corona discharges on an unsteady flowfield. This unsteadiness is characterized by a shock pulsation at the reduced frequency St = fc.LS/u0 = 3.10 2 . We observe a complete alleviation of the shock unsteadiness when a negative discharge is generated at the spike tip. With positive discharges, the effect is weaker. In both cases the input power is less than 1W. Discharge imaging and current measurements suggest that the negative discharge is a Trichel pulse corona discharge, whereas the positive discharge possibly involves streamers. The possible channels of interaction between the discharge and the airflow are briefly discussed.