Simulation Database of 3-D Shock/Turbulent-Boundary-Layer Interactions: Influence of Separation Structure and Symmetry on Mechanisms of Unsteadiness

A large-eddy simulation database is generated to examine the mechanisms of unsteadiness in three-dimensional (3-D), swept, shock/turbulent boundary-layer-interactions (STBLIs). A Mach 4 double-fin (DF) interaction is added to the database of Mach 2 swept compression ramps (SCR) and sharp fins (SF). The separation structure of the DF differs from that of the SCR and SF, in that closure of the primary separation occurs due to the merger of the two streams, resulting in the appearance of new singular points in the surface flow, around which pockets of low-frequency unsteadiness is observed. These singular points are not found in the simple 3-D interactions (SCR and SF) which exhibit quasi-conical mean-flow symmetry, without prominent low-frequency unsteadiness. However, the compound 3-D interaction (DF) necessitates a breakdown of quasi-conical symmetry which alters the separation structure. The associated appearance of additional singular points reflects the introduction of new (longer) length scales to the flow which allow for new (lower frequency) mechanisms of unsteadiness to manifest.