Modeling of High-Speed Boundary-Layer Transition Across Wide Mach Number Regimes

Hypersonic boundary-layer transition prediction technique plays a critical role in the aerodynamic and thermal protection design of supersonic/hypersonic vehicles. To enhance the Mach number applicability of transition prediction models and meet modern aircraft design requirements for multicondition and high-precision predictions, this study improves the calculation methods of key variables required for constructing the Mack second-mode timescale in the transition-turbulence prediction model proposed by Qiao, L., Xu, J., Bai, J., and Zhang, Y. [“Fully local transition closure model for hypersonic boundary layers considering crossflow effects,” AIAA Journal, Vol. 59, No. 5, 2021, pp. 1692-1706. https://doi.org/10.2514/1.J059765 ]. Specifically, temperature correction was implemented for momentum thickness calculation to better reflect the overall flow characteristics of boundary layers. The correlation between boundary-layer thickness and momentum thickness was recalibrated by comprehensively considering Mach number effects and temperature effects under different wall conditions (adiabatic walls and cooled/heated walls). Additionally, inflow disturbance effects were incorporated to improve model adaptability to various experimental environments. After the model modification, validations were conducted through several wind-tunnel test configurations under various Mach numbers, Reynolds numbers, and wall temperature conditions. Results demonstrate that, compared with previous studies, the improved model performs well in transition prediction across a wider Mach number range, effectively validating the rationality and accuracy of the proposed modifications. This advancement establishes a more extensive application foundation for the overall aerodynamic design, thermal protection structure design, and flight stability evaluation of hypersonic vehicles.