Magnetically Driven Surface Discharges for Shock-Wave Induced Boundary-Layer Separation Control

This study investigates the impact of a magnetically driven surface plasma column (“snowplow arc”) on shock induced boundary layer separation. The surface plasma column appears as a transverse “arc” between two diverging electrodes which is driven by j x B forces so that it sweeps the gas near the surface either in the downstream direction or in the upstream direction. In the experimental setup, an oblique shockwave wave was generated using a ten degree wedge in a Mach 2.8 indraft tunnel. The shock wave impinged on the flat surface in close proximity to the plasma actuator. Experimental results revealed a coupling of the plasma column with the shock – boundary layer interaction region which resulted in a change in the location of the shock induced boundary layer separation point. In case of the body force j x B acting upstream, the separation point was seen to move upstream. In case of the downstream j x B body force, a very small coupling was observed and the separation point appeared largely unaffected. Various reasons for the absence of an interaction in the downstream direction are discussed, particularly including the ratio of the scale of the plasma column to the boundary thickness. A sapphire insert with embedded electrodes is under development to allow for a higher current which then may be more effective for the suppression of boundary layer separation.