Effect of various mountainous terrains on the aerodynamic characteristics of high-speed trains under cross wind

The non-uniform wind fields generated by complex mountainous terrains pose significant challenges to train operation safety. A validated numerical method was adopted to explore the effects of various mountainous terrains on the aerodynamic performance of high-speed trains under crosswind. Specifically, the wind flow characteristics, flow field around trains, and aerodynamic loads acting on trains under five typical mountainous terrain configurations were thoroughly investigated. The results indicate that variations in wind field along the railway line are primarily caused by the airflow acceleration at the side edge and wake disturbance at the wake of the mountains. Among these five mountainous configurations, saddle terrain demonstrates more pronounced flow acceleration and an extended wake region due to the smaller inter-gap distance between the two mountains. Although the trailing car experiences the smallest aerodynamic forces, it exhibits the highest sensitivity to terrain configurations. Under saddle terrain conditions, the lateral force and overturning moment of the tail car increase by 279.0% and 140.7%, respectively, compared to the flat ground case. The aerodynamic peaks are observed at the critical moment when the trailing car emerges from the mountain's sheltering effect. This substantial aerodynamic load increase stems from a longitudinal vortex initiating at the train's head. The vortex develops downward to the rear while maintaining close alignment with the body surface. Such persistent attachment induces a marked negative pressure surge specifically on the tail nose. The research provides a theoretical basis and identifies critical risk parameters for wind hazard prevention in mountainous railway operations.