Aerodynamic Effect On Running Safety And Stability Of High-Speed Train

With the improvement of train speed, not only energy consumption increases sharply as to the increasing drag, but also the interaction between train and air is aggravated when the train cruising inside tunnels or under strong cross-winds. A series of aerodynamic problems deteriating running safety and ride comfort arise and demand a prompt solution. As a result, the interaction between high-speed train and air becomes an important engineering problem related to safe operation of high-speed railway, and it is a key technical problem which must be solved in the development of high-speed railway in China.For the issue of the high-speed train aerodynamics in cross-winds or inside tunnels, research on interaction between high-speed train and air and the influence of aerodynamic forces on train running safety and ride comfort have been carried out by numerical method by taking the train, track and tunnel structures into consideration.Under the arbitrary Lagrangian-Eulerian framework, the numerical model for train aerodynamics is set up by the Finite Volume Method (FVM) based on Navier-Stokes equation and k-εtwo equation turbulence models; On the basis of vehicle-track coupled dynamics, the numerical model for train-track coupled dynamics has been set up; The moving boundary between train and air is dealt with the arbitrary Lagrangian-Eulerian method (ALE); A co-simulation of Vehicle System Dynamics (VSD) and Computational Fluid Dynamics (CFD) has been realized and finally the numerical model for interaction between high-speed train and air is set up.The characteristics of flow field, aerodynamic forces, and vehicle dynamic response under different wind speeds and train speeds have been studied by the above mentioned method. Analysis has been carried on how aerodynamic forces and moments change according to wind speed and train speed. The velocity and pressure distribution around the train has been studied. The effect of cross-winds on the dynamic performance of high-speed train has also been studied in this paper. The results show that the heading car has the lowest security among the train judged whether by derailment coefficient, reduction ratio of wheel-load, overturning coefficient or by wheel/rail lateral force. The critical speed of high-speed train is studied according to the heading car's safety index. The critical speed judged by reduction ratio of wheel-load is the minimum and over-conservative. The critical speed judged by overturning coefficient is the maximum and over-loose. In the results derailment coefficient, reduction ratio of wheel-load, and wheel/rail lateral force exceed their criterion value before the overturning coefficient reaches the dangerous limit. The critical speed judged by wheel/rail lateral force lies between the critical speed judged by reduction ratio of wheel-load and the critical speed judged by derailment coefficient.Numerical simulation has been carried on the characteristics of the aerodynamic forces and aggravated lateral vibration inside Sanyo tunnels by the numerical model for high-speed train and air. The results indicate that the lateral acceleration of the end car is larger than the middle car's; Corresponding to other motion mode of car body, the heading mode of car body becomes more prominent, these results are similar with the phenomena existing in the Shinkansen train operation inside Sanyo tunnels. Different from the situation that the heading car has the worst aerodynamic performance under cross-winds, the end car has the worst aerodynamic performance in the Sanyo tunnels judged whether by derailment coefficient, reduction ratio of wheel-load, or by overturning coefficient. Taking the length of streamlined train head, the width of car body, the bottom structure of car body, the tunnel block ratios, line interval, etc. into consideration, the effect of these factors on the train lateral aerodynamic performance has also been studied.