Nonthermal Plasma Mitigation of Shock Wave in Supersonic Airflow

A non-thermal technique using a plasma spike, generated by 60 Hz periodic electric discharge, for shock wave mitigation is presented. The experiments were conducted in a Mach 2.5 wind tunnel. A plasma spike was generated in front of a wind tunnel model; it led to a transformation of the shock from a well-defined attached shock into a highly curved shock structure, which had increased shock angle and also appeared in diffused form. As seen in a sequence with increasing discharge intensity, the shock in front of the model moved upstream to become detached with increasing standoff distance from the model and was eliminated near the peak of the discharge. The power measurements excluded the heating effect as a possible cause of the observed shock wave modification. A theory using a cone model as the shock wave generator is presented to explain the observed plasma effect on shock wave. The analysis has shown that the plasma generated in front of the model can effectively deflect the incoming flow; such a flow deflection modifies the structure of the shock wave generated by the cone model, as shown by the numerical results, from a conic shape to a curved one. The shock front moves upstream with a larger shock angle, matching well with that observed in the experiment.