Schlieren Visualization of Controlled Disturbances in Mach 5 Flow Over a Hollow Cylinder Flare

The formation and evolution of a broadband point source disturbance in a Mach 4.82 laminar flow is characterized over a 15◦ hollow cylinder flare model. A forcing strategy, commonly known as Localized Arc Filament Plasma Actuators (LAFPAs), which functions via thermal energy deposition is employed. The LAFPA serves as a point source and its extremely short duration (≈ 300ns) is used to create a broadband disturbance in the flow. By using high-speed schlieren imaging phase locked to the LAFPA discharge, the evolution of the generated wave packet is characterized at various downstream locations over the model. Spectral and modal analysis of the pixel intensity of schlieren images obtained without the use of LAFPA (baseline) confirms the presence of first mode waves occurring naturally in the flow. These waves compare well with oblique first mode waves predicted by LST. Analysis of schlieren images during forcing is used to visualize the interaction of the disturbance with the base flow. Novel experimental information about the off-body density disturbance reveals the location and spread of the disturbance as it convects in the laminar boundary layer and lifts off into the separated shear layer. The disturbances introduced by the LAFPA successfully increases the amplitude of the first mode waves compared to the baseline case.