Study on liquid film dynamics and aerodynamic characteristics of train-bridge system under wind-rain interaction effects using Eulerian-Lagrangian approach

This study investigated liquid film dynamics and aerodynamic performances of a high-speed train on bridges in rainy conditions using Eulerian-Lagrangian approach. The effects of rainfall intensity and train speed on liquid film distribution and dynamics as well as aerodyne mic performances of the train were investigated systematically. The spatial distribution of raindrops and liquid film properties on the train were examined, followed by analysis of rainfall/train speed impacts on aerodynamic characteristics of the train—including forces, pressure distributions and wake dynamics. Aerodynamic characteristics around the train and in the wake were quantified via probe points. It is found that rainfall intensity is the main factor for liquid-phase distribution on the train. Windward surfaces exhibit significant raindrop accumulation, with liquid film thickness synchronously increasing with both rainfall intensity and train speed. At 350 km/h, the maximum Liquid Volume Fraction increased by 243.9% as rainfall intensity rose from 100 to 500 mm/h. The maximum liquid film velocity increased by 43.21% when train speed rose from 250 to 350 km/h under 500 mm/h rainfall. While both rainfall and train speed influence aerodynamics forces of the train, train speed governs global variation trends. Leeward flow demonstrates heightened sensitivity to rainfall, exhibiting substantial disparities in velocity, pressure and TKE distributions. Flow disturbance amplitude at probe points progressively decays with increasing height.