Numerical Simulation Of Aerodynamic Noise Of CRH380B High Speed Train

With the continuous development of China's high-speed railway,some problems of high-speed railway have also appeared.While the train speed is continuously increasing,aerodynamic noise has become the main noise source of high-speed trains and has become an urgent problem to be solved.In the process of establishing and perfecting high-speed railway standards in China,the environmental noise standards along the railways have become stricter.Under this environmental standard,the speed of high-speed railways is relatively limited.In order to build faster high-speed trains,reducing aerodynamic noise should be one of the most important issues in the train design process.The aerodynamic noise is mainly caused by the pulsating pressure generated by the large and small vortex on the train when the high-speed train and the air are subjected to rapid friction.At this stage,the most common method for studying aerodynamic noise is to model high-speed trains and numerically simulate and analyze their motion processes.In this paper,the hybrid method of lighthill acoustic analogy theory is used to numerically simulate the aerodynamic noise of CRH380 B high-speed train.The sound source distribution of the surface dipoles of the following vehicles at different speeds and the sound pressure levels at different strong noise sources of the following vehicles are analyzed,and the data are compared with the above contents of the CRH1 and CRH2 high-speed trains.Calculate the noise distribution of the CRH380 B high-speed train in the far field,the lateral attenuation law,the sound pressure of the standard measuring point and the data comparison with some parts of the CRH1 and CRH2 high-speed trains.Accurately study and analyze the aerodynamic performance of the CRH380 B high-speed train.The main work contents and conclusions are as follows:The train model and flow field calculation model of CRH380 B high-speed train were established.The aerodynamics of the following vehicle surfaces were calculated by large eddy simulation method to simulate the external flow field during the actual running of the train,and the pulsating pressure of the train surface was obtained.The pulsating pressure of the body surface of the train is transformed into the dipole sound source of the train surface,and the distribution law of the surface dipole sound source is analyzed.At different speeds,the sound pressure level curve of the train surface is basically the same.Below 1000 Hz,the train surface is a strong noise source,and as the speed increases,the sound pressure level of the train surface gradually decreases.The sound pressure curve of the train surface is fitted,and the calculation formula of the dipole sound pressure of the train surface at any speed is obtained.The theory that the radiant energy of the train is proportional to the sixth power of the speed is verified.At the same time,the surface sound pressure levels of CRH1 and CRH2 high-speed trains are calculated.Among them,CRH2 has the bestaerodynamic effect and CRH1 is the worst.For strong noise sources,we focus on the analysis of the bogie,the joint of the car,the surface of the front,the tip of the nose,etc.After comparative analysis,the strong noise source is generally higher than the aerodynamic noise on the surface of the vehicle.For vehicles with better aerodynamic noise,the strong noise source area is different.Using the train surface dipole source as the boundary condition,the far-field aerodynamic noise distribution of the train,the directivity of the train's special surface,the lateral attenuation of the noise,the noise frequency domain at the standard measuring point,and the direct boundary element method are calculated and analyzed.Comparative analysis with CRH1 and CRH2 vehicles.As the frequency increases,the noise level of the noise around the train decreases,but the noise distribution is more uniform.In the case of frequency determination,as the speed increases,the train dipole source radiation distribution is farther,the distribution is more even,and the maximum sound pressure level gradually increases with the increase of speed.The directivity distribution outside the train better reflects the noise distribution on the train surface.At low frequencies,the main source of noise from trains comes from the front,rear and train connections.In the high frequency band,although the noise on the surface of the train is reduced,the distribution is relatively uniform.As the distance between the lateral measurement points of the train and the vehicle body increases,the sound pressure level of the train noise gradually decreases and decreases linearly.In the area close to the train,the sound pressure of the train noise drops rapidly.The sound pressure level spectrum curve at the standard measurement point of the train is the same as the average sound pressure level spectrum curve(A weighting)of the train surface dipole sound source,but lower than the average sound pressure level at the surface(A weighting).At 20 Hz to 400 Hz,the frequency increases with increasing frequency,and the sound pressure at the standard point is maintained at a certain level at 400 Hz to 1000 Hz,and starts to decrease gradually after 1000 Hz.Relative to the average sound pressure level(A weighting)at the surface of the train,the value of the sound pressure level spectrum curve at the standard measuring point is more intense near the point,because the data is monitored at the standard measuring point.It is derived from the aerodynamic influence of each part on the same point.The noise distribution is different everywhere,and the change at the measuring point is more severe.