Numerical Simulation Study On Aerodynamic Noise Of High-speed Train Under The Influence Of Ambient Wind

During the running of the train,the aerodynamic noise is proportional to the6～8th power of the train running speed.With the increase of operating speed,the aerodynamic noise will increase sharply,which will produce strong noise pollution to the external environment and affect the comfort of riding inside the train.Since the ambient wind is one of the significant factors affecting the aerodynamic noise of high-speed trains,a high-speed train model with a scaling ratio of 1:20 is used in this paper to solve the external flow field of high-speed trains through a delayed separation vortex model,and the FW-H equation is used to calculate the noise propagation and analyze the influence of the ambient wind on the external flow field structure,sound source distribution and far-field noise characteristics of high-speed trains.The main research contents of this paper are:(1)The numerical calculation method is verified to be grid independent.Firstly,a numerical simulation of the cylindrical winding problem with Reynolds number of90,000 is performed,and the total sound pressure level and the spectral-frequency curve of sound pressure level at the far-field measurement points are analyzed and compared.Secondly,the spatial discretization method and time step in the high-speed train aerodynamic noise problem are discussed and the grid-independence is verified.(2)The aerodynamic noise characteristics of high-speed trains during steadystate operation are discussed.The external flow field structure of high-speed trains is analyzed by velocity field,vortex field and Q iso-surface,and the contribution of quadrupole sound source to the total aerodynamic noise is discussed based on the calculation results of broadband noise model,and the spectral characteristics of dipole sources and the distribution characteristics of far-field aerodynamic noise are analyzed.(3)The influence of different ambient winds on the aerodynamic noise characteristics of high-speed trains is studied.After aerodynamic analysis,it is determined that the aerodynamic noise problem is of practical significance when the speed of the ambient wind is within 10 m/s.The results of the study on the flow field,sound source and far-field noise characteristics show that: influenced by the ambient wind,the turbulent pulsation in the outflow field of high-speed trains increases,the sound source intensity on the leeward side of the train is higher than that on the windward side,and the sound source intensity at the bottom of the train increases more.ambient wind within 10 m/s changes the acoustic directivity of high-speed trains in the wake region and increases the aerodynamic noise by 2.1 d B～8.7 d B.(4)Under the influence of ambient wind,the changes of aerodynamic noise of high-speed trains with different operating speeds were analyzed.The effect of ambient wind on the outflow field and aerodynamic noise of high-speed trains running at 70 m/s,75 m/s and 80 m/s was investigated by simulating the ambient wind with a transverse wind of 5 m/s.The results show that the influence of the ambient wind on the outflow field,the distribution of sound sources and the intensity of sound sources decreases as the operating speed of high-speed trains increases;the acoustic directivity of the pneumatic noise of high-speed trains does not change significantly when the trains are running at speeds between 75 m/s and 80 m/s,and the total sound pressure level of the far-field noise measurement points changes within 2 d B.This paper investigates the pneumatic noise characteristics of high-speed trains under the action of ambient wind,and the research methods and results can provide theoretical guidance and technical support for the pneumatic acoustic design of highspeed trains.