Improvements to the Medida–Baeder Transition Model for Three-Dimensional Transonic Flows

This study presents enhancements to the laminar–turbulent boundary-layer transition model based on the Spalart–Allmaras turbulence model for three-dimensional transonic flow conditions. The baseline model has been extended to incorporate both compressibility corrections and stationary crossflow transition effects. The compressibility correction is based on the Arnal–Habiballah–Delcourt simple model, addressing Tollmien–Schlichting instabilities. The crossflow transition extension employs an empirical correlation developed by Langtry. Additionally, the intermittency transport equation was modified to mitigate nonphysical relaminarization by introducing a nonlocal variable for the eddy viscosity diffusion effect. The extended model has been systematically validated against test cases, including the NLF(2)-0415 swept wing, the sickle wing with spanwise-varying sweep angles, the NASA Common Research Model–Natural Laminar Flow (CRM-NLF) configuration under transonic conditions, and the Hover Validation and Acoustic Baseline (HVAB) rotor in hovering conditions. Results demonstrate significant improvements in accurately predicting transition onset locations, which affect the shock location for the CRM-NLF and the figure of merit in the HVAB hovering rotor.