Study On Characteristics And Mitigation Measures Of Micro-Pressure Wave In High-Speed Railway Tunnel At 400 Km/h

The compression waves produced generated when the high-speed train enters a tunnel propagate along the tunnel near to the sonic speed and create a pulse wave at tunnel exits,usually called micro-pressure wave.The micro-pressure wave cause structural vibration and noise problems,which seriously affect the surrounding environment and residents’lives.With the rapid development of high-speed railway technology,the intersection speed of trains in the tunnel has reached 405km/h,and the existing tunnel hood is difficult to meet the needs of micro-pressure wave mitigation.Therefore,it is necessary to carry out research on the mitigation measures of the micro-pressure wave at 400 km/h.In this paper,ICEM CFD is used to divide the mesh of the train,tunnel,and tunnel hood.The method based on the combination of ANSYS FLUENT sliding mesh and dynamic layer technology simulates the train passing through the tunnel with different structures at 400km/h,and its mechanism and mitigation effect on the micro-pressure wave are analyzed.The key points are as follows:(1)The mitigation mechanism of the tunnel hood at the entrance is analyzed.The effects of tunnel hood length,clearance area,number,and location of perforated on micro-pressure wave is compared.The tunnel hood at the entrance divides the rising process of the initial compression wave into several stages through oblique cutting,enlarging the section,and perforation,and increases the rising time of the initial compression wave to alleviate the micro-pressure wave.The tunnel hood at the exit reflects part of the energy of the initial compression wave into the expansion wave by increasing the flow channel area and reduces the strength of the micro-pressure wave by the pressure relief effect generated by the perforated.Compared with the non-perforated tunnel hood,the perforated tunnel hood is more sensitive to the variation in the length of the tunnel hood,and the micro-pressure wave intensity remains unchanged after exceeding a certain value.With or without a perforated tunnel hood,there is an optimal clearance area to minimize the intensity of the micro-pressure wave,which is related to the tunnel length.The number and location of perforated affect the variation of the micro-pressure wave.The tunnel hood at the entrance with different clearance areas(155m~2,175m~2,and 200m~2)can meet the requirements of 400km/h micro-pressure wave mitigation.(2)The mitigation mechanism of the tunnel hood at the exit is analyzed.The effects of clearance area,the slope of the inclined section,and the number of perforated on the micro-pressure wave were studied.The results show that the tunnel hood reflects part of the energy of the initial compression wave into the expansion wave by increasing the clearance area to reduce the intensity of the micro-pressure wave.Based on the enlarged model,increasing the oblique section can increase the area of the compression wave radiating outward and decrease the micro-pressure wave.Finally,the micro-pressure wave is relieved by increasing the pressure relief effect produced by the perforated.The intensity of the micro-pressure wave decreases with the increase of the slope and the number of perforated but increases with the increase of the clearance area,it can also alleviate the micro-pressure wave and provide a new idea for the design the of tunnel hood.(4)The effects of the location,length,and area of the tunnel branch and the length,location,area,and angle of the inclined shaft on the micro-pressure wave are analyzed.The results show that the strength of the micro-pressure wave is not sensitive to the change in the location and length of the tunnel branch,and increasing the area of the branch can effectively alleviate the micro-pressure wave.Short inclined shafts can reduce the intensity of the micro-pressure wave,but the micro-pressure wave is not sensitive to the change of the inclined shaft location and angle.Increasing the inclined shaft area can also alleviate the micro-pressure wave.The research in this paper can provide a reference for the design of tunnel hood at the speed of 400 km/h and provide solid technical reserves for the construction of a high-speed railway network in China.