Plasma effect on shock waves in a supersonic flow

An experimental study of the plasma effect on the structure of an attached conical shock front appearing at the front end of a cone-shaped model has been carried out in a Mach 2.5 stream. The tip and the body of the model are designed as the cathode and anode, which are separated by a conical-shaped ceramic insulator providing a 5 mm gap for gaseous discharge. The electric field intensity near the cathode is enhanced by the sharpness of the tip. The experimental results show that the diffused discharge can produce plasma distributed symmetrically around the tip in the region in front of the shock wave. It is observed that such plasma can cause shock wave moving upstream with its shock front detached from the model. The shock front is also becoming more and more diffusive and having an increasing shock angle as seen in the shadow video graphs of the flow. A physical mechanism of the observed plasma effect on this type of shock wave is also presented.