Influence of windbreak distance on the aerodynamic performance of high-speed trains by Large Eddy Simulation

The distance of the windbreak from the centerline of the track affects the safe operation of high-speed trains in windy areas. In order to clarify the influence and mechanism of different distances of windbreaks on the vortex interference in the flow field, based on the large eddy simulation and overlapping grid, present work carried out numerical simulation of aerodynamic performances of high-speed train with four different distances of the windbreak from the centerline of the track (l = 6, 8, 10, and 11 m). The results indicate that when the high-speed train travels across the non-transition section, the lateral force coefficients and overturning moment coefficients of the train at four distances show basically a trend of decreasing and then increasing with the increase of the distance. The aerodynamic force/moment coefficients are the smallest among four situations studied, and the lateral force coefficients decrease by 23%, 76%, and 48% for the leading, middle, and end cars, respectively; the overturning moment coefficients decrease by 48%, 77%, and 63%, respectively, meanwhile the train has the smallest lateral force coefficient vibration amplitude, and the main peak frequency is concentrated in the range of 0 ～ 10 Hz. When the high-speed train passes through the transition section, the changes of lateral force coefficient and overturning moment coefficient of the train at l = 10 m are also relatively smaller. It shows that, among the four different distances, the aerodynamic safety of the train is the best at l = 10 m, as well the wind protection effect of the windbreak. However, it should be noted that when the train passes through the transition section, the surrounding flow structure undergoes complex changes. The middle car experiences the least impact from the combined effects of high-speed airflow and train-induced wind, while the aerodynamic performance fluctuations of the leading and end cars are more pronounced. The present research can be used as a reference for the construction and maintenance of windbreaks on high-speed railways.