Development of Plasma-based Controlled Disturbances for the Study of Boundary Layer Transition and Shock Boundary Layer Interaction

This paper focuses on the development of plasma actuators for the study of boundary layer transition and shock boundary layer interaction (SBLI). Experiments are performed in an indraft wind tunnel at Mach 5. The employed devices are more commonly known as Localized Arc Filament Plasma Actuators (LAFPAs) and are known to function via thermal energy deposition. Actuators are characterized in a vacuum chamber before being introduced into the tunnel with a newly installed Mach 5 nozzle (Re_u = 2.7 × 10⁶ m^-1). Plasma actuation is applied to the laminar boundary layer on the wind tunnel sidewall with supporting calculations from linear stability theory. Synchronized wall pressure (PCB) measurements and Z-type schlieren imaging are used to evaluate the plasma-generated disturbances and their influence on instability waves both with and without SBLIs. Both the frequency and wavelength of the plasma-generated wave packets were found to be in good agreement with LST predictions for the second mode in the boundary layer case. The addition of an SBLI reduced the dominant frequency of the instability waves and increased the wavelength.