Numerical Study Of Mechanism Of Turbulent Flow Induced Noise Of High-speed Train Pantographs And Possible Noise Reduction Measures

China boasts the greatest commercial operational speed and the longest operating mileage of high-speed rail in the world;the main trunk lines have been running at up to 350 km/h.Aerodynamic noise will be disruptive to nearby residences and train passengers at this operating speed.Since high-speed train pantographs are the primary source of aerodynamic noise,it is important to investigate the rheological noise mechanism of high-speed train pantographs and develop an appropriate noise reduction strategy based on this knowledge.A large eddy simulation method is used to numerically simulate the three-dimensional,constant-property,non-constant,incompressible turbulent flow of air around the pantographs of high-speed trains.The reliability of the numerical method is verified by selecting the cylindrical winding flow and its noise problem that can be analogous to the pantograph rods.Based on this,the effects of operating speed and rod form on the pantographs for high-speed trains’ near-field flow field characteristics and far-field noise characteristics are compared.Since the numerical simulation results of flow-generated noise are greatly influenced by the geometric shape of the object,this paper first considers the influence of the degree of simplification of the pantograph geometric model on the numerical simulation calculation results,so the original geometric model of the pantograph is simplified to different degrees.The study shows that after further simplifying the pantograph geometry model,the maximum increase of sound pressure level at 7.5m in the far field is about 6d B(A),with a maximum increase of about 6.6%,the maximum increase of sound pressure level at 25 m in the far field is about 4d B(A),with a maximum increase of about 3.6%.The noise caused by fluid flow around the pantograph is directly related to the operation mode and speed of the pantograph.To study the mechanism of the noise caused by fluid flow around the pantograph,the flow field and noise characteristics of the pantograph under different operation modes and operating speeds were comparatively studied.The study shows that when the pantograph is closed for operation,the vortex in the area of the arm bar grip is dominated by small-scale vortex.The sound pressure fluctuation amplitude at 25 m in the far field increases by about 10 Pa,and the peak sound pressure level in the high frequency band increases by about5 d B(A).When the pantograph is running,with the increase of running speed,the vortex intensity on the surface of the arm pole increases,the fluctuation amplitude of the sound pressure level curve at 25 m in the far field decreases,the frequency of the extreme value of the sound pressure level becomes higher,the frequency of the extreme interval decreases,the maximum interval frequency is about 100 Hz,and the maximum value of the sound pressure level is about 102 d B(A).Two noise reduction schemes for elliptical rod and elliptical torsional rod pantographs are proposed based on the noise performance of each pantograph component,and the differences in flow field and noise characteristics between the original rod pantograph and the noise reduction scheme are compared.The study shows that the elliptical torsion bar pantograph has a better noise reduction effect in the far field under different operating speeds.At the operating speed of 400 km/h,the sound pressure level at 7.5 m in the far field can be reduced by about 6d B(A),with a maximum reduction of about 5.5%,at 25 m in the far field,the sound pressure level can be reduced by about 5 d B(A),with a maximum reduction of about 4.2%.The results of this paper provide a certain reference for the development of new low-noise pantograph structures.