Study On Micro-pressure Wave Noise Characteristics Of Railway Tunnel Portal At Higher Speed

With the large-scale construction and speedup of China's high-speed railways and the increase in the speed of train operations,there have been a number of aerodynamic phenomena that jeopardize the safety of railways.The phenomenon of micro-pressure waves in the openings is one of them.The micro-pressure wave at the entrance is an infrasonic wave.When the intensity is high,it will produce a sonic boom phenomenon,which will cause serious damage to the residents and buildings near the tunnel entrance.It has become a phenomenon that must be controlled at the tunnel entrance.The intensity of micro-wave pressure at the opening is mainly related to the two processes of the initial compression wave generated by the train entering the tunnel and the radiation of the initial compression wave to the opening.Therefore,this paper studies the influence of different factors on the formation of the initial compression wave and the propagation process,and studies the radiation process when the initial compression wave propagates to the hole.Based on certain assumptions,this paper uses the characteristic line equations and adopts a one-dimensional compressible non-stationary unequal entropy flow model.On this basis,the method of dividing and processing the grid type is improved.The transient friction factor is added to simulate the initial compression wave and the propagation process in the tunnel.The difference between the calculated results of this paper and the actual vehicle experimental results and literature results is within the allowable value,which verifies that the calculation method and the calculation result of this paper are more accurate and can reflect the actual situation.According to the propagation characteristics of the initial compression wave in the tunnel,this paper applies the modified generalized Riemannian characteristic line method to the calculation of the initial compression wave,and increases the accuracy of the initial compression wave propagation in the tunnel,effectively reducing the numerical consumption.Scattered.This article takes CR400 AF as the research object and studies the characteristics of the initial compression wave generated by the train entering the tunnel.Through the improved initial compression wave generation and propagation procedures,the effects of train speed,different tunnel lengths,and different group lengths on the propagation of the initial compression wave in the tunnel are analyzed.Different factors were obtained to analyze the propagation characteristics of the initial compression wave in the tunnel.This paper evaluates the intensity of micro-wave pressures emitted by the acoustic formula to the outside of the outlet end of the tunnel when the initial compression wave propagates to the exit end of the tunnel.It provides data basis for subsequent research and improvement of tunnel buffer devices and provides useful reference value.