Volumetric Characterization of Experimental Flowfield in a Double-Fin SBLI at Mach 3

Shock-Wave/Boundary-Layer Interaction (SBLI) presents inherent challenges in the aerodynamics of supersonic and hypersonic vehicles, including flow separation, unsteady pressure loads, structural vibrations, and inlet unstart. This study experimentally characterizes the fully volumetric (3-dimensions, 3-components) mean flowfield of a symmetric Double-Fin SBLI with a fin angle of 15° at Mach 3. A novel Scanning Stereoscopic Particle Image Velocimetry (S-SPIV) technique is employed to capture three-component velocity field using streamwise-aligned planes through a custom traverse system, carrying the PIV setup that links laser and cameras. It enables continuous scanning where the resulting data are spatiotemporally averaged to reconstruct a volumetric velocity field for three-dimensional flow analysis. In particular, the reconstructed volumetric velocity field captures the interaction of swept λ-shocks generated by the sharp fins and reveals their detailed topological evolution. These multi-λ-shock interactions lead to the formation of a Shock-Tangle, and their impact on the flowfield is examined in detail, including the associated slip surface formation. Moreover, within the boundary layer, a longitudinal counter-rotating vortex pair is identified in the vorticity field, and its streamwise alignment with the centerline separation observed in surface oil flow visualization is examined. Additionally, another counter-rotating vortex pair is observed from the surface oil flow visualization beneath the separation shock, offering additional insight into the footprint and structure of the near-wall separated region. These high-fidelity experimental analyses provided improved understanding of the fin-induced SBLI, with practical implications for the development of high-speed aircraft.