Over the Centerline Scaling and Spanwise Characteristics of Blunt-Fin- and Cylinder-Generated Shock-Wave/Turbulent Boundary-Layer Interactions

An investigation of a shock wave/turbulent boundary-layer interaction (SWBLI) generated by cylinders and blunt fins was performed. Emphasis was placed on using numerical methods, namely Reynolds-averaged Navier–Stokes (RANS) and large eddy simulations (LES), although companion wind tunnel experiments using high-speed schlieren imaging and oil-flow visualization were also performed. Scaling effects on the centerline separation distance (S) and the lambda-shock triple-point height (h_tp) as a function of the ratio of diameter to boundary-layer thickness (d/δ) were investigated; a new scaling law is proposed that normalizes these parameters as S/δ and h_tp/δ, which yielded highly-agreeable correlations for both linear and exponential best-fit curves, even when including data from the archival literature at vastly different flow conditions. Spanwise effects of the evolution of key flow features were also investigated, consisting of the separation line and bubble, pressure rise, and vortices. These flow features are most severe at the centerline and rapidly lose strength in the outboard direction. Separation was limited in the outboard extent to about ±2d-3d, and the dynamic behavior of separation was identical to that on the centerline. The separation line persists as a disturbance in the pressure distribution even without flow separation, and its curvature linearizes at around ±6d. Lastly, the advantages and limitations of RANS and LES as a method for gathering pertinent information on this SWBLI were described in the context of the generated data of interest to a vehicle designer.