Railway lines in the Xinjiang wind area face severe wind disasters year-round, which seriously affects the safety and economy of the railway in China. Therefore, the wind characteristics and statistics of wind-induced accidents along the Xinjiang railway lines are presented and the basic research route for evaluating the train running safety under crosswinds and effective measures to improve the windproof performances of trains are proposed, which are meaningful to deal with wind-induced train accidents. Based on this research route, a series of numerical simulations are conducted to evaluate train safety and the corresponding measures are provided. The results show the following. The running safety of the train under crosswinds mainly depends on the aerodynamic loads acting on the train. The relationships between the safe speed limit and train type, the load weight, the embankment height, the road cutting depth, the railway line curve parameters, the yaw angle and other factors are obtained. The critical wind-vehicle speed relationship, as well as the engineering speed limit value under different running conditions, are determined. Large values of the aerodynamic and dynamic indices mainly appear in special locations, such as near earth-embankment-type windbreak walls, shallow cuttings and the transition sections between various types of windbreak walls. Measures such as increasing the height of the earth-embankment-type windbreak walls, adding wind barriers with reasonable heights in shallow cuttings and optimizing the design of different types of transition sections are proposed to significantly improve the safe speed limits of trains under crosswinds.

The aerodynamic drag of pantograph system hinders the increase of train operating speed, which can be reduced by the covering structure proposed in this study. Exploring the drag reduction mechanism of covering structure is critical. An IDDES method based on the SST κ–ω turbulence model was utilized to study the effect of covering structure on aerodynamic performance of high-speed train. The results show that the covering structure reduces the overall drag by 5.6% for 3-car train-set since the impingement of incoming flow on the surface of sinking platform is alleviated. The aerodynamic drag of the middle car is significantly reduced while that of the tail car increases due to higher pressure on the train joint surface caused by the covering plates. The turbulence of the flow field surrounding sinking platform is suppressed by weakening the flow separations from cavity edge. Vortical structure changes occur to the vortices shed from the leading edge of cavity because the front covering plate delays the process of flow separation, further leading to the alteration of dominant frequencies for folded pantograph. The covering structure will decrease the oscillation of lift force by 24.74% and 37.14% for lifted and folded pantograph.

Double unit trains running at high speeds may create additional aerodynamic challenges due to two streamlined structures with close proximity, exploring the aerodynamic performance of double unit trains is now critical. In this study, detached eddy simulation (DES) approach was employed to study the aerodynamic performance and the nearby flow patterns of a double unit train, whose results were compared and analyzed with that of a single-unit train with a same length. The results showed that the coupling method could change the aerodynamic drag on each car and tended to increase the overall drag of the double unit train. The lift force of the front car near the coupler was significantly increased. Similar slipstream distributions were found around the front half single and double-unit train except in a region close to the coupler. Due to the coupling structure, the slipstream of the rear half of double unit train was much stronger compared to single unit train. The vortex region behind the double-unit train was much wider than that of the single-unit train and was accompanied by greater vortex-shedding.

The perforated shrouds have been proposed to control cylinder flows, while the effects and mechanisms at different Reynolds numbers (Res) remain unclear. Three-dimensional numerical simulations are conducted in this paper to compare the aerodynamic performance of the flow around a smooth cylinder and a shrouded cylinder at Re of 3900 and 1.4×105. The results indicate that the drag of the perforated shrouded cylinder is reduced by 30.8% at the high Re, while increased by 26% at Re of 3900 compared with the smooth cylinder. Differently, the lift oscillations of the cylinder are greatly weakened by 83.3% at the Re of 3900 and 98.5% at the Re of 1.4×105, which implies the wake oscillations are nearly eliminated at the Re of 1.4×105. Further analysis exhibits the near wake region is elongated along the mainstream, with significantly recovered pressure. Especially, the greater pressure loss owing to outer shrouds even leads to the negative drag of the inner cylinder at the high Re. In addition, the incoming flow is broken up by outer shrouds, and different flow patterns appear in the gap. The discernible vortex pairs occur in the gap at the Re of 3900, while as Re increases to 1.4×105, the quantities of small-scale vortex weaken the impact on the inner cylinder. The shear layer characteristics are elucidated by Lamb vector curl and Kelvin–Helmholtz instabilities. The vorticity stretching and tilting in the shear layer of the shrouded cylinder is much weaker at the high Re. Generally, the energy for shear layer instabilities at low frequencies is diminished with the presence of perforated shrouds. However, the energy at higher frequencies is strengthened at the low Re.