Preliminary Study On Simulating Pressure Waves Produced By Trains In Urban Regional Railway Tunnel

With the development of the economy of nations around the world,urban rail transit has been paid more and more attention,especially the construction and development of urban subway.Taking the subway cost into account,the general subway tunnel sections are smaller,the air-tightness of subway trains are is less sealed.Therefore,with the continuous increase of the train speed,many aerodynamic problems will be caused and can not be overlooked,such as tunnel pressure waves,drags of train and pressure comfort in the train.Thus,the study of subway tunnel pressure waves is necessary for development and improvement of urban rail transit in the future.When the subways train running in the underground tunnels,the situation is the same as the high-speed train passing through the tunnel and the air flow caused by the train operation is subject to limited space of tunnel.However,when considering the tunnel structure and the train operation mode,the study of subway trains running in the underground tunnels is more complex.On one side,there are stations in the tunnel,and ventilation shafts are located on both sides of the station or between stations in the tunnel.On the other side,There are multiple trains running in the tunnel,and the trains should accelerate,decelerate,uniform operate and even park at the station.So it is not easy to simulate the pressure wave while the train running in the underground tunnel.It is rather difficult to simulate the pressure wave of subway tunnel by three-dimensional numerical simulation because of the complex of the tunnel structure and the train operation mode.Therefore,in this paper,one-dimensional unsteady compressible non-homentropic flow model is used to establish airflow equations.and the method of characteristics of generalized Riemann variables is adopted to solve a set of equations.On the basis of relevant scholars’ researches,the method and the procedure of simulating pressures while trains running in the underground tunnels is investigated in the paper.This paper takes two trains running in four shaft tunnel with constant speed tracking operation as example.Combining the reflection diagram of train tracks and waves to analyze the rationality of train pressure waves,the influence of the train speed and departure time interval on the outside pressures of the vehicles are studied.The following conclusions are drawn: the new pressure waves will be generated while pressure waves launching to the shafts position;when two trains running inside a tunnel,the pressure fluctuations induced by the train will affect each other;Shortening succession time and reducing vehicle speed appropriate can slow down the maximum pressure values outside train.