Modeling of freestream disturbance intensity effects on crossflow instability induced transition in high-speed boundary layers

The development of hypersonic boundary-layer transition and turbulence prediction models within the Reynolds-averaged Navier–Stokes (RANS) framework remains a key research focus and challenge in high-speed aerodynamics, owing to the need for a balanced integration of computational efficiency, predictive accuracy, and applicability to complex engineering configurations. In 2025, Zheng et al. proposed a streamwise transition–turbulence prediction model capable of covering a broad Mach number range under varying freestream disturbance intensities; while demonstrating satisfactory performance across diverse hypersonic transition scenarios, this model does not account for crossflow-instability-dominated transition. To address this limitation, the present study focuses on modeling hypersonic boundary-layer transition driven by crossflow instability. Guided by wind tunnel experimental data, the freestream disturbance intensity is explicitly incorporated into the crossflow-induced transition criterion. A local closure for nonlocal variables is then formulated using similarity solution analysis. This enhancement is subsequently integrated into the four-equation transition–turbulence prediction framework originally proposed by Zheng et al. The improved model is applied to a set of canonical wind tunnel benchmark cases, including the HIFiRE-5 elliptic cone, the HyTRV lifting body, the X-33 lifting body, and an inclined straight cone. Predicted transition locations are in good agreement with experimental measurements, confirming both the accuracy and robustness of the proposed modeling approach.