Study On The Effect Of Pressure Waves During Two Freight EMU Passing By Each Other In A Tunnel

With the improvement of China's technical and economic level,the rapid development of e-commerce industry,the freight EMU came into being.The aerodynamic problems caused by the tunnel also need to pay attention and research.During the process of entering the tunnel,the freight EMU will has the phenomenon of import wave and tunnel pressure wave due to the restrictions of the tunnel wall surface.Therefore,it is very necessary to study the tunnel aerodynamics problem of the freight EMU.Based on finite element volume method and overset gird method,this dissertation is based on STAR-CCM+,a widely used computational fluid dynamics software with high accuracy,and combines SST k-? high Reynolds number turbulence model in the numerical simulation.The data obtained from the experiment and the data obtained by numerical simulation are put together for comparison,analysis and summary,so as to demonstrate the applicability and rationality of the method used in this paper.The main research contents and conclusions are as follows:(1)The paper studies the pressure distribution characteristics during two freight EMU passing by eachother in a Tunnel.The pressure fluctuation caused by the tunnel intersection is the superposition of the pressure pulses produced at tunnel entrance and produced by trains passing by is proved,and the superposition of the compression wave or the expansion wave in the tunnel.These waves overlap in the tunnel and form complex characteristics with time.(2)This paper also analyses the formation and distribution characteristics of tunnel entry waves.The entrance wave of the tunnel consists of negative and positive pressure pulse waves generated when the head and tail of the train enter the tunnel.This paper mainly analyzes the production mechanism and propagation characteristics of the tunnel entry wave caused by a freight EMU into the tunnel,as well as its spatial distribution characteristics,and concludes that it has attenuation effect with increasing radial distance.(3)Research has been conducted to obtain the variation law of different train speeds on the pressure wave in the tunnel,the pressure wave on the train surface,and the tunnel entry wave.The research shows that: under different speeds,the waveforms of pressure waves inside the tunnel,pressure waves on the surface of the train,and inlet waves of the tunnel are the same,but the faster the vehicle speed is,the earlier the peak time occurs,and the peak increases with the increase of the vehicle speed.(4)Analyze the effect of different tunnel lengths on the pressure waves in the tunnel,the pressure wave on the surface of the train,and the import wave generated by a freight EMU.The change of the length of the tunnel leads to different running time in the tunnel of a freight EMU.By comparing pressure peak,it is concluded that the pressure wave in the tunnel and the pressure wave pressure on the car body surface under the condition of shorter tunnel length have larger peak values.Since the tunnel entry wave is generated when a freight EMU enters the tunnel,the length of the tunnel has no influence on the imported wave.The above research contents and results have enriched discussion on the development of high-speed rail freight of our country.It is a basis for further research on the tunnel aerodynamics problems generated by a freight EMU and provides a useful reference.