Recent studies have shown atmospheric plasma discharges to be an effective means of air flow control. If in subsonic conditions the plasma's effect is explained by a transfer of momentum from the charged particles to the neutral ones, in supersonic conditions it seems that the effects are mainly of thermal origin but some authors think that this effect is not the only one to act. This paper presents experimental results of stagnation pressure, spectroscopic emission and drag performed in a rarefied Mach 2 flow over a flat plate model with a half-wedge leading edge. Changes caused by a negative dc discharge located on the upper surface of the flat plate are investigated in two cases. In the first case the negative potential is applied on the upstream electrode and in the second case it is applied downstream. The second electrode is grounded. The measurements carried out indicate two opposite effects depending on the localization of the negative potential.

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The present work is an attempt to clarify the physical interpretation of the changes in flow parameters and dynamic loads induced by an electric discharge in the vicinity of a flying body. The particular case considered here is a sharp flat plate in a low-density flow at Mach 2. The problem has been studied both experimentally and numerically. It is concluded that the change in wall temperature due to the discharge explains best the changes observed in the distribution of Pitot pressure. The observed changes in dynamic loads due to the discharge cannot be explained by the distribution of wall normal and tangential stresses. Coulomb forces between the gas and the electrodes mounted on the wall are probably also involved.