Numerical Analysis Of Aerodynamic Noise Of CRH380A High Speed Trains

With the development of high speed railway,high speed train running speed continues increasing,and increases the noise of train.Because aerodynamic noise is 4-8 times proportional to the running speed,which may become the main noise source.Based on the Lighthill acoustic analogy theory,through Large Eddy Simulation Method and Finite Element Method combined with Perfect Matching Layer Boundary Condition&Higher Order Element,aerodynamic noise of CRH380A high speed trains is analyzed.The main work and results of this paper are as follows:1.The external flow field of the high speed train is calculated by using the Large Eddy Simulation Method.The surface pulsation pressure data of the vehicle body is converted into the surface dipole sound source,and the distribution of the surface dipole sound source is analyzed.High speed train surface dipole sound source exists in a broad frequency brand,especially between 50-1100Hz.Expression for the average surface dipole sound pressure level under different speeds is derived,which matched with the "6 party" theory.Bogie,car connection,front baffle,rear nose,etc.are main high speed train noise source locations;2.Through Finite Element Method combined with Perfect Matching Layer Boundary Condition&Higher Order Element,external space aerodynamic noise distribution,aerodynamic noise transverse attenuation law,noise level at the far field standard point in frequency domain and time domain of CRH380A high speed train caused by surface dipole sound source are analyzed.The directivities of external space aerodynamic noise are inconsistent in different directions.As the distance from the sound point to the body increases,the sound pressure level at the sound point is attenuated by the logarithmic law.The standard point noise and the body surface sound source have the same frequency domain characteristic.When train running under 300km/h,the equivalent sound pressure level at standard measurement point is 85.90dB,which is close to the experimental result.With the increase of train speed,the noise level at the standard point also increases;3.According to the train surface dipole sound source and the standard of measuring points noise of CRH380A,CRH2 and CRH3 high speed train,CRH2 performs best,then CRH380A,and CRH3 is the worst one.The equivalent average sound pressure level at the standard measurement point in time domain of CRH380A is only 2.64dB higher than CRH2,and which of CRH3 is 7.14dB higher than CRH2;4.The variation of the noise distribution in the external space after considering the quadrupole sound source is studied.The result shows that low-frequency noise distribution is mainly concentrated in the tail and upper of the train while high-frequency noise distribution turns to the body and front,which is similar to the noise distribution only consider dipole sound source;the quadrupole sound source enhances the external noise,especially for high frequency noise.The sound pressure level at the standard measuring point increase by about 10%because of the quadrupole sound source;5.The propagation law of aerodynamic noise of high speed train under the sound barrier is analyzed,and the influence of different sound barrier conditions on the external space noise is explored.After installing vertical sound barrier,noise lateral spread trend weakened obviously,the sound pressure level at standard point decreased about 3-10dB in the whole frequency range,and noise reduction effect of high-frequency noise is better than that of the low-frequency noise.The height of the noise barrier has a great influence.With the increase of lm in height,the insertion loss of the sound barrier is increased by 1.2dB,and the 3050mm high from top of the sound barrier to rail surface is the most suitable choice considering both construction cost and noise reduction effect.The noise reduction effect of different shapes of the noise barrier is close,but the noise reduction effect of the Y type sound barrier is best,and compared to the insertion loss of the vertical sound barrier which is increased by 1.19dB.The sound absorbing property unit on the surface of the sound barrier can enhance the noise reduction ability,and the stronger absorption properties will bring more additional increase to noise barrier insertion loss.