Frequent extreme wind events in China's coastal regions pose severe challenges to the aerodynamic performance of high-speed trains passing through tunnel portals under strong winds. To reveal the distribution patterns of bay winds at high-speed railway tunnel portals in coastal areas and enhance the operational safety of high-speed trains, this study systematically investigates the bay wind effects and train aerodynamic responses at coastal high-speed railway tunnel portals by combining the RNG k-ε turbulence model and the sliding mesh technique. A computational fluid dynamics (CFD) prediction model, based on actual terrain and a high-speed railway tunnel section, was established to dynamically simulate the process of a high-speed train passing through the tunnel portal.

Based on the research findings regarding the mountainous flow field and train aerodynamic loads, it was discovered that under incoming flow with wind direction angles of 90° (due west) and 270° (due east), the flow acceleration behavior induced by the mountain slope resulted in the maximum wind speed at the tunnel portal, which increased by 26.5% and 29.0%, respectively, compared to the incoming wind speed. When the train passes through the tunnel portal section, the aerodynamic loads fluctuate drastically, and the fluctuation amplitude of the head car's aerodynamic load is significantly higher than that of the middle and tail cars. Further analysis revealed a significant positive correlation between the embankment height and the fluctuation amplitude of the train aerodynamic loads, and a linear function provided a good fit for the relationship between aerodynamic force fluctuation amplitude and embankment height. This research can provide a solid theoretical basis and engineering guidance for the route selection and wind-resistant design of high-speed railways in coastal areas.