Conditions and a physical mechanism for plasma mitigation of shock wave in a supersonic flow

Wind tunnel experiments show that plasma generated by on-board discharges can significantly weaken the shock wave generated in front of a 30° half-angle truncated-cone model placed in a Mach 2.5 flow. Experimental results indicate that, in order to give rise significant effect on shock waves, plasma has to be generated in the region upstream of the baseline shock front and has to have a symmetrical spatial distribution with respect to the axis of the model. Experimental results also exclude the thermal effect as a possible cause of the observed shock wave mitigation. A physical mechanism of the observed nonthermal plasma effect on shock waves is presented. Analysis shows that a symmetrically distributed plasma spike in front of the shock can effectively deflect the incoming flow symmetrically. The required electron density of the plasma spike is estimated.