Triggering Shock Wave Positions by Patterned Energy Deposition
Philip S. Andrews, Philip Lax, Sergey B. Leonov
Abstract
The problem considered in this work is shock wave (SW) positioning control in shock-dominated flows. Experiments are conducted to investigate the triggering effect of patterned near-surface electrical discharges on SW reflection from plane walls. In the wind tunnel, M=4, P0 = 4 bar, a solid wedge SW generator is mounted on the upper wall. Q-DC filamentary electrical discharges were arranged on the opposite wall, so that the SW from the wedge impinged on the plasma filaments that are arranged flow-wise in either a row of three or a single central filament. Within the supersonic flow, narrow subsonic areas are actuated by electrical discharge thermal deposition, resulting in pressure redistribution, which, in turn, relocates the reflection of impinging SW to a predefined position. Mie scattering, schlieren imaging, and wall pressure measurements are used to explore the details of plasma-SW interaction. Using Mie scattering, the three-dimensional shape of the SW structure is mapped both before and after electrical discharge activation. Plasma-based triggering mechanisms are described in terms of the physical principles of flow control and a criterion for determining the effectiveness of the flowfield control.