Research On Aerodynamic Noise Of High-speed Train Considering Ground Effect

With the increase of the train running speed,the aerodynamic noise problem of the high-speed trains has become increasingly prominent and has seriously affected the ride comfort of high-speed trains.When the running speed of the train reaches 300km/h,the aerodynamic noise will become the main noise source of high-speed trains,so the aerodynamic noise has become a important problem that people pay close attention to.Based on the Lighthill's acoustic analogy method,considering ground effect,the external aerodynamic noise of CRH3 high-speed train is calculated in this paper.The main work contents are as follows:(1)A numerical simulation model of aerodynamics calculation of the CRH3 high-speed train considering the ground effect is established,the simulation model includes a head nose-coach,a middle coach,a tail nose-coach,a pantograph and 6 bogies.To consider the effects of ground effects,increasing the accuracy of calculations,the necessary structures including roadbeds and rails are built under the body.(2)Firstly,the steady-state flow field around the high-speed train is calculated.The standard ?-? model is used for steady-state calculation.The steady-state aerodynamic characteristics of the train flow field at the speeds of 200km/h,250km/h,300km/h and 350km/h are calculated.At the same time,the broadband noise sources are calculated based on the results of steady-state,the surface pressure maps and the surface sound power level clouds of the train are achieved.The results show that the surface pressures and the surface acoustic power levels are relatively large in the head of train,the front bogie and the pantograph.(3)The steady state simulation results are used as initial conditions,the external transient-state flow field of the high-speed train is calculated based on the Large Eddy Simulation(LES),the pulsating pressure on the surfaces of high-speed train are obtained.Based on the Lighthill theory of acoustic analogy,the aerodynamic noises of high-speed trains at different speeds are calculated by using of the FW-H method.The aerodynamic noise characteristics in the far field,under the train and the bogie area are calculated and analyzed.The results show that the bogies,the pantograph,the head and the tail of the train have a great influence on the aerodynamic noise of the train;The noise of bogie area is larger under the train,the sound pressure level at the front bogie center of the head vehicle is the highest,and then the aerodynamic noise at the rear of the bogie is larger than the noise at the front.(4)By analyzing the aerodynamic noise spectrum and 1/3 octave,the results show that the aerodynamic noises of the train are broadband noise and there are no obvious main frequency.With the speed of the train increasing,the sound pressure levels of the monitoring points increase;the change law of the A-weighted sound pressure levels at various monitoring points is similar,and the main differences is that the A-weighted sound pressure level values is different.With the speed of the train increasing,the dominant frequency of the A-weighted sound pressure level tends to move toward higher frequencies.