Modulation of a ramp-induced shock wave/boundary layer interaction through extended frequency range pulsed discharge

Our experimental study explored the impact of pulse discharge energy deposition, across a wider frequencies ranging from 5 kHz to 20 kHz, on a Shock Wave/Boundary Layer Interaction (SWBLI) at a Mach number of 2.47. Using high-speed schlieren imaging, Planar Laser Scattering (PLS) and Focused Laser Differential Interferometry (FLDI), we analyzed the characteristics of discharge-induced energetic eddies and their impact on SWBLI. The Spectral Proper Orthogonal Decomposition (SPOD) was employed to scrutinize the structural transformations of the flow field under the influence of pulse discharge. Our findings indicate that pulsed discharge significantly alters the flow field by propelling the separation shock upstream, with this effect intensifying as the discharge frequency increases. Additionally, the discharge diminishes the fluctuation intensity of the separation shock and the shear layer, and it reduces the low-frequency spectral energy of the separation shock. SPOD analysis revealed that at high discharge frequencies, the flow field dynamics shift from the low-frequency oscillations of the separation shock to the motion of vortices along the boundary layer, which interact with the shock waves. The control efficacy of pulsed discharge on SWBLI demonstrates remarkable consistency and intensity at frequencies of 10 kHz or higher, whereas a notable attenuation in effectiveness is observed at 5 kHz. This reveals a critical frequency threshold beyond which flow characteristics change markedly, primarily seen in the progressive weakening of the separation shock. However, further frequency increases beyond this point yield diminishing returns in SWBLI control effectiveness.