Aerodynamic Performance And Running Safety Of High-Speed Train On Double-Track Embankment Under Crosswind Condition

The accidents of trains blown away from track or overturned by strong wind have happened many times in the world. With the increase of train speed, strong wind has become a big and chief obstacle to the running safety of high-speed train. As the aerodynamic performance of high-speed train on double-track embankment is very poor in crosswind, the problem of running safety is very serious. Therefore, it is necessary to study the aerodynamic performance and the running safety of high-speed train in crosswind in details, when it is running on double-track embankment.The study of aerodynamic performance and safety of train in crosswind is briefly reviewed at first. Based on the computational fluid dynamics, a three-dimensional aerodynamic model of high-speed train running on a double-track embankment under crosswind condition is set up. The corresponding train system dynamic model is established on the basis of multi rigid-body system dynamics. The flow structure around the train and the pressure distribution on the surface of the train are showed. Influences of the train speed, crosswind speed and height of embankment on the aerodynamic performance and the running safety of high-speed train is studied. The aerodynamic performance and the running safety of high-speed train on the windward track of embankment are compared with those on the leeward track. Besides, the comparison between two different configurational trains is carried out. The influence of crosswind on the running behaviour of high-speed train is investigated. The effects of aerodynamic forces on running safety are compared. The running safeties of high-speed train are investigated with and without considering the incline moment and the yaw moment. The critical safety running speed in crosswind is determined.Numerical results show that the aerodynamic performance and the running safety of high-speed train in crosswinds are basically controlled by the head car. With the increase of train speed, crosswind speed, embankment height, the aerodynamic performance and the running safety both become poor. When the high-speed train is travelling on the windward track, the aerodynamic performance and the running safety are better than those on the leeward track. With the increase of crosswind speed, differences of the aerodynamic performance and the running safety between two configurative trains become large. The crosswind has greater influence on the wheel/rail lateral force than the wheel/rail vertical force. The running safety is closely related to the running balance state of the vehicle which is changed by the crosswind. Influences of crosswind on the dynamic performance of the head car and the tail car are mainly determined by the side force and the yaw moment. As for the middle car, it is dominated by the side force. In the vehicle system dynamic model, the incline moment and the yaw moment are suggested to be taken into consideration. The dynamic performance is more sensitive to the car body mass in crosswind than that without crosswind. When the head car is a motor car with full load, the lateral wheelset force is usually the first index exceeding the safety limit among all safety indices. When the head car is an empty trailer car, the wheel load reduction ratio is always the first index going beyond the safety limit. The critical safety running speed of high-speed train with the empty head car is much lower than that with the full load head car. Therefore, the head car is suggested to be a motor car with full load. When the high-speed train is running on flat ground, the critical safety running speed is higher than on embankment. On the low embankment, it is higher than on the high embankment.