Flow Structure and Heat Transfer Characterization of a Blunt-Fin-Induced Shock-Wave/Laminar Boundary-Layer Interaction

Abstract

An experimental investigation of a blunt-fin-induced shock-wave/laminar boundary-layer interaction (SBLI) has been conducted at a nominal Mach number of 4.The experimental data is supplemented by computational results from Reynolds-averaged Navier Stokes computations provided by Raytheon Missiles & Defense.Two blunt fins with a leading-edge diameter of 9.525 mm (3/8”) and sweep angles of 0 and 45 degrees were tested on a flat plate with unit Reynolds number 4.3×10^6 m−1 (Re_x= 2.7×10^5). The unswept fin produces significant separation extending x/D ≈ −5.5 upstream of the fin leading edge. Mach number contours indicate two horseshoe vortices wrapping around the unswept fin base. The swept fin SBLI features are subdued in comparison, but qualitatively similar, with evidence of horseshoe vortices also present. Temperature sensitive paint (TSP) was employed to investigate the near-wall flow structure and estimate surface heat flux. Prominent features include various reattachment lines associated with vortices in the separated region, as well as shock-shock interactions and shear-layer impingement on the fin leading edge. Increasing the sweep angle altered the flow topology considerably, including the location and magnitude of maximum heat flux. The surface distribution of Stanton numbers are derived, demonstrating complex interactions with a rich set of flow physics to be investigated in future work. Amongst other findings, the influence of sweep has a moderate impact on peak heat transfers, with Stanton numbers reaching 0.022 and 0.035 for the swept and unswept fins respectively.