Aerodynamic performance and flow dynamics of High-Speed train under crosswind: Effect of turbulence model

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This study employs Reynolds-averaged Navier–Stokes (RANS), improved delayed detached eddy simulation (IDDES), scale-resolving hybrid (SRH), and large eddy simulation (LES) turbulence models to conduct a comparative numerical analysis of the aerodynamic load characteristics and surrounding flow field structure of a high-speed train at a Reynolds number of 250 000 and a yaw angle of 30°. The influence of the Gamma Re-Theta transition model and grid resolution on the computational results is investigated. The findings indicate that the LES method based on the wall-adapting local eddy-viscosity (WALE) model performs well with sufficiently refined grids, exhibiting small errors compared to wind tunnel tests. Without using a transition model, the RANS, IDDES, and SRH turbulence models are unable to accurately capture the near-wall flow characteristics at any grid resolution, consequently failing to accurately predict the pressure and pressure fluctuation distribution on the train surface. This fundamental deficiency stems from the models' difficulty in capturing instabilities within the free shear layer. When a transition model was employed, both the IDDES and SRH turbulence models demonstrated improved capability in predicting the train's aerodynamic performance. Furthermore, SRH exhibited superior grid adaptability, and it maintained excellent performance even on coarse grids and achieved computational accuracy comparable to that of the LES model. The core conclusion of this study confirms that the SRH model, leveraging its robust performance and potential for significant computational cost reduction, emerges as a promising approach for studying highly separated external flows at high Reynolds numbers.