Effects of favourable downstream pressure gradients on separated shock-wave/boundary-layer interactions

Abstract

Shock-wave/boundary-layer interactions (SWBLI) strongly influence the aerodynamic behaviour of many aerospace, propulsion and transportation systems. They have therefore been studied intensively — with different methods, configurations, and test facilities. Regions of favourable pressure gradient are often placed downstream of the SWBLI region., e.g. to prevent wind-tunnel blockage. To be able to better understand their effect and compare cases from varying sources, a joint experimental–numerical study of a supersonic compression/expansion corner flow is carried out. A high-resolution long-time numerical simulation complements particle-image velocimetry measurements, both using the same configuration and conditions. Derived setups without the downstream expansion corner are also explored; both for the same compression-corner angle and for a ramp angle inducing a separation bubble of the same size as for the original compression/expansion configuration. Results demonstrate that the topology and very low-frequency dynamics of the separation bubble developing over the compression corner are altered by the downstream expansion corner. Differences are mainly found for the downstream motion of the shock/shrinking of the separated region and extend downstream of the reattachment point up to the expansion corner.