Aerodynamics Research On High-Speed Train Passing Through A Tunnel

With the continuous increase of train speed,the interaction between train and air have became very intense. In train aerodynamics problems, aerodynamics effects of train passing through tunnel are extremely prominent. High-speed train passing through the tunnel will produce a series of significant aerodynamic effects such as transient pressure, micro-pressure wave, train piston wind, aerodynamic forces and aerodynamic noise etc,which affect passengers in comfort and living environment around the tunnel. In China there are a large number of tunnels on the railway line. Researching on aerodynamic problems of high speed train passing through tunnel is necessary in the context of raising train speed on existing railway line. How to use the new technology means, raise the level of design, is an important task for the researchers.Building a experimental device to simulate the interaction between trains and tunnels is very difficult and expensive, so the use of computers in the numerical analysis of tunnel aerodynamic effects is very valuable.Create finite element model applicable to the aerodynamic performance using the high-speed train as original model.Make use of large scale computational fluid dynamics software SC/Tetra to simulate high-speed train passing throuth tunnel which bases on a three-dimensional, unsteady, turbulent, compressible flow.Comparing calculation results with test data.the variation trend is consistent.This indicates that the computation model and the computed result are credible.The result of numerical simulation shows that:the aerodynamic problems occurring when train travels at high speed in tunnel are more complicated and serious,compared with the open air traveling. The aerodynamic drag on a train traveling in a tunnel can significantly increase, compared with that in the open air,the pressure on the side walls of head train,central train and tail train increase 863%,897%,952%.When a HST enters a tunnel, a compression wave is formed ahead of the train which propagates along the tunnel at a nearly sonic speed.A part of the compression wave is reflected back from the exit of the tunnel as an expansion wave. A complex wave interaction occurs inside the tunnel due to successive reflections of the pressure waves at the exit and entry to the tunnel.These pressure waves cause large pressure transients resulting in fluctuating loads on the train causing deformation to train body and discomfort to passengers, a part of the compression wave leaving the tunnel exit gives rise to an impulse noise which affect living environment around the tunnel.It is necessary to predict these pressure transients to design trains and tunnels, and to improve the passenger comfort.