In a supersonic engine inlet, the adverse pressure gradient caused by an oblique shockwave generated by an inlet cone interacts with low momentum boundary layer air at the inlet wall to create a region of recirculating flow called a separation bubble. This separated region reduces the effective area of the engine inlet, requiring a larger inlet to get the desired mass flow rate. As a result the engine must be larger and heavier.
Over the past year, investigations have been done into the viability of controlling this oblique shockwave/boundary layer interaction with plasma actuators, using a supersonic wind tunnel simulating an engine inlet. Plasma actuators were considered for this application due to their ability to generate streamwise vortices in the flow. Vortices move low momentum boundary layer air out into the free stream and high momentum free stream air down into the boundary layer, thus increasing the momentum in the interaction region and reducing or eliminating separation.
A test section containing a 10° shock generator and adjustable floor was designed and installed into an existing supersonic wind tunnel. Plasma actuators were tested at various frequencies and distances to the oblique shock impingement point, and their effect was visualized using schlieren photography.Air Force Research LaboratoryNo embarg
