Shockwave induced turbulent boundary layer separation control with plasma actuators

In this study we report Acetone Planar Laser Scattering (PLS) visualization of the boundary layer structure inside Mach 2.6 indraft wind tunnel at Princeton University. The aim is to better understand the surface plasma control of shockwave boundary layer interaction (SWBLI) region and separation. These experiments are designed to evaluate magnetically driven surface plasma actuators for effective shockwave induced boundary layer separation control within supersonic inlets. Static pressure measurements and Schlieren images of the shockwave boundary layer interaction region were reported earlier and it was shown that when a weak shock generator (10°) is used to generate the impinging shockwave, while no separation occurs without plasma control, a small current plasma column (< 100mA) at 1-3 Tesla is enough to induce separation by flow retardation in the interaction region. Strong shockwave from a (14°) generator was shown to induce separation and experiments are done at high currents 100-250 mA; for flow acceleration in the interaction region. At these relatively high currents, the plasma actuation is able to delay the incipient separation. Also, in the absence of magnetic field, no change in the flow structure is seen, indicating marginal role of joule heating in the process. Acetone PLS imaging provides boundary layer flow structure in relative detail and direct evidence of separation control.