Effect of a plasma in supersonic flow Eliminating the shock wave instability using a plasma
This study investigated the effect of plasma on a shock wave, with a view to attenuating the effect (reducing the wave drag) or controlling its instability. In the experiments carried out in the Meudon center's R1Ch wind tunnel (Mach 3), a plasma was created around the nose of a truncated cone equipped with a spike at the front used, as an electrode. The other electrode consisted of the metal part of the model behind the conical part, made of an insulating material (Macor). Figure 1 shows the model in the wind tunnel, along with the negative corona discharge (the spike is the cathode) used to act on the shock generated upstream of the truncated part.
Model with truncated conical head
[fitted with a spike used as
a cathode]
in a supersonic flow (Mach 3).
The plasma thus created
by the negative discharge acts
on the shock to stabilize it.
In practice, when the spike is longer than the distance from the shock wave generated to the body, and when there is no plasma, shock wave instability occurs that is brought out using flash Schlieren photography.
Activation of the high voltage circuit produces a corona discharge oriented forward when the central spike is negatively polarized (case in the figure above). The Schlieren photographs then show that the shock wave's unsteadiness is stabilized. The stabilization can be observed about 2 ms after the start of the discharge.
The experiment thus showed the direct influence of a very low energy (less than 1 watt) cold plasma, visible in the figure above, on the shock wave generated upstream of a truncated conical head equipped with a spike. If there is no plasma, the spike generates an unsteady shock wave. Activation of the discharge fixes the shock in a stable position.
The direct influence of a very low energy (less than 1 watt) cold plasma on a shock has thus been demonstrated. This study opens the way to technical innovations for controlling shock unsteadiness.
Publication
Elias P.-Q., Chanetz B., Benay R., Coponet D., Packan D. et Larigaldie S., On board Plasma Generation in Pulsating Supersonic Airflow, 40ème Colloque AAAF d’Aérodynamique Appliquée (Toulouse 21-23 Mars 2005)
Model with truncated conical head in a supersonic flow (Mach 3).
The plasma created by the positive discharge allows for display
of the shock wave downstream.
