Research On Aerodynamic Noise Source Characteristics Of High Speed Trains

With the rapid development of high-speed railway and continuous promtion of train speed,the aerodynamic noise of high-speed trains has increasing impact on ride comfort and the surrounding environment.It has become one of the current problems to be solved.Therefore,the research on prediction and control of the aerodynamic noise has great significance.In this paper,aiming at the problem of aerodynamic noise in near-field and far-field of high-speed train,a computational fluid aerodynamic model of' high-speed train is established based on the related acoustic theory and numerical calculation method,and the aerodynamic noise outside the train is calculated and analyzed.The main research contents are as follows:(1)According to the geometric model of CRH3 high-speed train,the local complex area 'is simplified without affecting the main structure of the model.The Hypermesh software is used to divide the grid to establish an aerodynamic simulation model of high-speed EMU with the eight-car grouping,the main components include:the head car,the tail car,6 middle cars,2 pantographs and 16 bogies.The calculation domain is set according to the actual situation,and the corresponding boundary conditions are imposed.(2)Using the standard ?-? turbulence model,the steady flow field characteristics of the train running at 250 km/h,300 km/h,350 km/h and 400 km/h are calculated and analyzed,respectively.The sound power levels of the train surface are calculated based on the broadband noise source model,and the noise distribution characteristics of key positions on the surface of high-speed trains are analyzed.(3)The steady results of the eight-car grouping are taken as the initial condition,the transient flow field characteristics of the train are calculated based on the large eddy simulation,and the aerodynamic noise of the high-speed train is calculated and analyzed by the FW-H acoustic analogy integration method.The body,bogies,and pantographs are used as noise sources respectively,the noise contribution and frequency spectrum characteristics in the near-field region are compared and analyzed at different speeds,and the causes of airflow disturbance in local area and its influencing factors are analyzed.(4)The body,bogies and pantographs are used as noise sources respectively,the radiation noise of the far field for each source are calculated at different speeds,the noise contribution and spectrum distribution characteristics of each noise sources in the far-field region are compared and analyzed.(5)Based on the far-field radiated noise of local noise sources,the far-field noise of each local noise source is superimposed according to the noise superposition principle,the superposition result is basically consistent with the noise of the whole train as a far-field noise source,which verifies that the local noise sources of high-speed train conforms to the sound source superposition principle,this provides new ideas and methods for high-speed train noise research.(6)The ICFD module of Actran software is used to import the transient flow field data of high-speed train and convert the transient flow field data to obtain the frequency domain data of the outflow field by using of the Fourier Transform.The far-field noise of the head car,tail car and middle cars are analyzed based on the finite element-infinite element method,and so the noise spectrum and the sound pressure level cloud map are obtained.