Electrical properties of a slidding discharge in supersonic air flow

International audienceRecent studies have shown atmospheric plasma discharge to be an effective means of air flow control. In subsonic air flow DC discharge or Dielectric Barrier Discharge are used to produce “ionic wind”. This momentum is used to modify characteristics of the air flow (Moreau et al.). In supersonic airflow the discharge induces gas heating. This energy addition to the flow results in an increase in the local sound speed that leads to expected modifications of the flow (Bletzinger et al.). Nevertheless some experiments have shown some anomalous flows around the body and anomalous shock waves structures in cold plasma. In order to explain these experiments some teams works on the hypothesis of the existence of non thermal effect in non equilibrium weakly ionized gases (Klimov et al.). This non thermal mechanism should be responsible for this anomalous effect. Flow control of supersonic air flow by means of surface plasma discharge is a new topic of our laboratory. The first step is to study the discharge in a supersonic air flow. In a precedent work we have shown that the plasma discharge created by means of DC potential difference applied between two thin electrodes placed on the surface of a flat plate, was very unstable in a supersonic air flow. Indeed the discharge goes into an arc regime as soon as the air flow velocity increases. In this paper we show how we obtain a stable plasma discharge in a supersonic air flow (M=1.8) with help of a third electrode and a combination of DC and AC high voltage potential. Experimental results will be presented. We will show the influence of different parameters like the frequency, DC potential, ac potential on the discharge curren