Study On Aerodynamic Characteristics Of High Speed Train And Its Impacts On Environment

The theme of railway development is "safe,comfortable,environmental,fast"in the world today.As the train speed increases,which improves the transportation efficiency of the railway system and saves travel time for the citizens,the interaction between high speed train and environment,which not only puts forward higher requirements for running safety,but also poses a greater challenge to the surrounding environment is more complex and severe.In order to adapt to development that high speed train is safer,more comfortable,more environmentally friendly and more rapid,aerodynamic characteristics of high speed train running in crosswind conditions,meeting conditions and impacts induced by the train on the surrounding environment were studied thoroughly by numerical simulation method.The main works are as follows:(1)The governing equations and numerical calculation methods of Computational Fluid Dynamics(CFD)were introduced.Numerical results of the high speed train flow field by using several kinds of commonly used turbulence models were compared and analyzed which determined the SSTk-?model as the turbulence model used for the following study.(2)The computational domain model(following is called CDM)of train running in crosswind based on certain CRH3 model was set up.Aerodynamic characteristics of a high speed train under crosswind was studied by the method of wind tunnel simulation.The aerodynamic coefficients variations of each coach under different running speed(200?400 km/h)or wind speed(0-40 m/s)were obtained.(3)The CDM of train meeting in crosswind was set up.The meeting process of both same trains passing at the same speed in the open line was simulated by using dynamic mesh method(following is called DMM),obtaining variations of the aerodynamic coefficients of each coach under different running speed(250-450 km/h)or wind speed(0-40 m/s),emphatically analyzing the variations of aerodynamic characteristics in the windward and leeward side,pointing out that there is a certain similarity between the both trains at the aspect of flow field pressure variation of the train's surface or space near it when passing by each other without crosswind.(4)The CDM of train meeting in tunnel was set up.The meeting process of both same trains passing at the same speed in tunnel was simulated by using DMM,obtaining variations of the aerodynamic coefficients of each coach and tunnel wall pressure under different running speed(300?400 km/h),emphatically analyzing the variations of tunnel wall pressure and aerodynamic drag of head coach and tail coach through the Mach wave propagation theory,pointing out that there is a certain similarity between the both trains at the aspect of flow field pressure variation of the train's surface or space near it when passing by each other in tunnel,but the spatial flow field structure has no geometric central symmetry.(5)The symmetric CDM of train running without crosswind was set up.The running process of a single train without crosswind was simulated by using DMM,obtaining the variations of train wind velocity,of which magnitude and direction were emphatically analyzed under different running speed(350?500 km/h).Two safety domain decision methods,by which trackside safety domain under different running speed was divided according to two safety indexes were put forward.The power function relation between speed values and safety limit values is determined.Finally,the recommended setting distances of the trackside fence under different running speed were given.