Three-Dimensional Flow Topology of Double-Fin Shock-Wave/Boundary-Layer Interaction Using Volumetric Velocity Measurements

Shock-Wave/Boundary-Layer Interaction (SBLI) poses inherent challenges for supersonic/hypersonic aircraft, including flow separation, unsteady pressure loading, vibration, and engine unstart. A symmetric Double-Fin is a canonical configuration often used in high-speed aircraft components and subsystems, such as vertical tails and ramjet/scramjet inlets. Experiments to investigate SBLI induced by Double-Fin with fin angles of 10 ∘ , 12 ∘ , and 15 ∘ , resulting in increasingly stronger interactions, are conducted at Mach 2. Using Scanning-Stereoscopic Particle Image Velocimetry (S-SPIV), three-dimensional, three-component velocity fields are acquired, facilitating a deeper exploration of highly three-dimensional multi-shock interactions. The evolution of this complex flow, such as the interaction of λ -shocks generated by the fins, is comprehensively examined for improved understanding of the governing flow physics. In particular, the interaction between the front-foot of the reflected-shock and the fin-shock gives rise to a distinct, stronger shock referred to as Shock-Tangle , accompanied by a localized low-velocity region. Three-dimensional slip surfaces are identified at shock–shock intersections, and a streamwise counter-rotating vortex pair forms in the near-wall region downstream of the interaction. Through S-SPIV, key flow features are resolved in unprecedented detail, enabling quantitative comparison of the Double-Fin and Single-Fin flow topologies and revealing differences in quasi-conical symmetry and shock organization. The findings advance the fundamental understanding of fin-generated SBLI, with practical implications for current and next-generation high-speed vehicles.