Investigation of a Nanosecond Sliding Surface Discharge in Time-Dependent Supersonic Air Flow in a Channel

The regimes of development of a 500 ns sliding surface discharge are experimentally studied in time-dependent supersonic air flows in the channel of shock tube with a rectangular cross-section. The Mach numbers of the shock waves were from 2.30 to 5.00 at the initial air pressures from 2 to 100 Torr and the Mach numbers in the flow were from 1.18 to 1.66. A 100 mm-long sliding surface discharge was initiated at a given moment of time in different stages of the time-dependent supersonic flow after plane shock wave diffraction on an obstacle and in a quasistationary flow past the obstacle in the presence of an inclined shock wave. The discharge current and spatial radiation characteristics were analyzed. The high-speed shadowgraphy of the flow fields was carried out at the frequency up to 525 000 frames per second. The numerical modeling of the channel flow was performed within the framework of the Navier-Stokes equations. The comparison of the experimental and numerical results made it possible to establish the correlation between the parameters of a low-density zone formed as a result of the interaction between the oblique shock wave and a boundary layer and the regime in which the discharge current proceeds. The flow structure in the channel is analyzed after the discharge initiation, when a near-semi-cylindrical shock wave is formed. The comparison of the experimental and numerical results shows the thermal energy released in the discharge current region amounts to from 0.15 to 0.36 J.