Study On The Effective Noise Reduction Region Of The Inside Surfaces Of The Noise Barrier On The Railway Bridge

For more than ten years continuous exploration and development,Chinese high-speed railway construction has made remarkable achievements.However,with the continuous improvement of the train speed,noise pollution along the railway line has increased dramatically.Excessive noise has a significant impact on the normal life along the railway line,which is attracted extensive attention.The aerodynamic noise of high-speed train is a key factor restricting the train speed-increasing.Therefore,studying the spatial distribution of aerodynamic noise of high-speed train is helpful to reduce aerodynamic noise.The two-dimensional unsteady incompressible Reynolds averaged Navier-Stokes equations combined with RNG(Renormalization Group)k-? turbulence model are used to calculate the flow field around the two-dimensional high-speed railway bridge in the crosswind.The velocity of the crosswind is set as 10,15 and 20 m/s,the wind attack angle is taken as 0°,±1°,±2° and ±3°.The surface of railway bridge is taken as the aerodynamic noise source surface.The time-histories of areodynamics sound pressure of monitoring points are calculated by FW-H(Ffowcs Williams-Hawkings)equations.The overall sound pressure levels of the monitoring points are obtained by Fast Fourier Transform method.The analysis results show that the aerodynamic noise is closely related to the crosswind.The overall sound pressure levels for the crosswind speed of 20m/s is 3.4dB~9.5dB much higher than that for the wind speed 10m/s and 15m/s.The wind attack angle has obvioust impact on the aerodynamic noise of the bridge,the overall sound pressure levels of monitoring points in the positive attack angle is 1.3dB~3.5dB much higher than that in the negative attack angle.The sound pressure levels of aerodynamic noise of the bridge is much higher in the low-frequency range(within 100Hz)than other frequencies.On the basis of the two-dimensional high-speed railway bridge,in order to simulate the aerodynamic noise of the two-dimensional vehicle-bridge,the high-speed train is running on the windward side track.The analysis shows that the overall sound pressure levels of monitoring points in the leeward side are 1.0dB~3.3dB much higher than that in the windward side.The sound pressure levels of aerodynamic noise of the two-dimensional vehicle-bridge system is much high for frequencies within 1000 Hz.The three-dimensional vehicle-bridge system model is established,MRF(Multiple Reference Frames)method is adopted to simulate the effect of the crosswind and the train induced wind.The velocity of the crosswind is set as 20m/s,and the speed of train is taken as 0,200,250 and 300km/h.The flow field of the vehicle-bridge system is simulated by the three-dimen-sional unsteady incompressible Reynolds averaged Navier-Stokes equations combined with RNG k-? turbulence model.The surfaces of the high-speed train and bridge are taken as the aerodynamic noise source surface.The time-histories of aerodynamic sound pressure of monitoring points are calculated by FW-H equations.The overall sound pressure levels of monitoring points are obtained by Fast Fourier Transform method.The analysis results show that the overall sound pressure levels of monitoring points in the leeward side are 1.1dB~14.8dB much higher than that in the windward side for 4 cases.The overall sound pressure levels of areodynamic noise of the monitoring points are increased with the train speed,when the train is running on the windward side track.The sound pressure levels of the aerodynamic noise is much high for frequencies within 1000 Hz.The effective region of the noise reduction is obtained by the sound pressure level of areodynamic noise of the monitoring points,which is 0.5m~2.0m on the top of rail.