Aerodynamics of recirculating flow control devices for normal shock/boundary layer interactions

Passive control-based methods of controlling shock/boundary layer interactions consist of a porous surface covering a cavity or a plenum located in the region of the SBLI. The present study focuses on the flowfield downstream of a Mach 1.42 SBLI over various passive control devices such as a conventional porous plate, a microporous plate, streamwise slots, conventional mesoflap array, and a hybrid flap array. Qualitative analysis of the various control devices investigated was achieved with spark shadowgraph visualizations and surface oil-flow visualizations. Quantitative analysis was accomplished by measuring surface static pressure distributions, boundary layer velocity profiles, and pitot pressure distributions in the subsonic diffuser downstream of the SBLI. The flowfield downstream of a slot-controlled and a hybrid flap array-controlled SBLI were found to be highly three-dimensional, while the downstream flowfields were predominantly two-dimensional for the remainder of the control devices. It was found that only the conventional mesoflap array had an improved total pressure recovery, both in the near-field and further downstream in the subsonic diffuser, as compared to the uncontrolled, solid-wall SBLI.