Study On Aerodynamic Effect Of Hood With Multiple Openings At The Outside Tunnel Of High-speed Maglev Transit

The offline of the 600km/h Maglev Test Vehicle marks that china has made important achievements in key technology fields of high-speed maglev transit.Because there is no tunnel in the maglev line in operation in china,there is little research on the micro-pressure wave at the exit of high-speed maglev tunnel.The amplitude of micro-pressure wave is approximately proportional to third power of the train speed.When the maglev train passes through the tunnel at a speed of 600km/h,the micro-pressure wave is very intense,which will seriously affect the living environment of residents around the tunnel.Therefore,the research on the reduction of micro-pressure waves is important for the development of china's high-speed maglev railway.Meanwhile,the amplitude of the micro-pressure wave is proportional to the maximum pressure gradient of the initial compression wave at the exit of the tunnel.It is very effective to slow down micro-pressure wave amplitude by setting the hood with openings.In this thesis,numerical simulation is performed by using the computational fluid dynamics(CFD)software STAR-CCM+based on high-speed maglev test vehicle model in our country and single-hole double-track tunnel with a clearance area of 140m~2.In the process of simulation,the overset grid technique,Reynolds time-averaged(RANS)turbulence simulation method and SST k-?two-equation turbulence model were used to solve the three-dimensional,unsteady and compressible turbulent flow of the external air when high-speed maglev train enter the tunnel.And the following research work was conducted.(1)Taking the high-speed maglev train entering the flat tunnel of without hood as the research object,the formation mechanism of the initial compression wave is analyzed when maglev train enter the tunnel.(2)Based on the analysis of the characteristics of the initial compression wave in the flat tunnel of without hood and the tunnel of hood without openings,the maximum pressure gradient of the initial compression wave can not be reduced by setting a circular hood without openings with equal cross section to the tunnel at the outside tunnel.(3)By comparing the pressure gradient curves of the initial compression wave in the tunnel of hood with 1m square openings,the tunnel of hood with 0.4m square openings and the tunnel of hood without openings,the results show that there is a big peak value of the pressure gradient curve of the initial compression wave in the tunnel of hood without openings,while the pressure gradient curve of the initial compression wave in the tunnel of hood with 1m square openings and 0.4m square openings is decomposed into two small peaks,thus avoiding the occurrence of the maximum pressure gradient value.(4)The maximum pressure gradient value of the initial compression wave in the tunnel of hood with 1m square openings is 65.65%lower than that in the flat tunnel of without hood,and the maximum pressure gradient value of the initial compression wave in the tunnel of hood with 0.4m square openings is 59.97%lower than that in the flat tunnel of without hood.The effect of hood with 1m square openings is better than hood with 0.4m square openings in terms of reduction of maximum pressure gradient value of the initial compression wave in the tunnel.(5)The characteristics of pressure wave in hood with 1m square openings and 0.4m square openings are studied and the maximum pressure and the maximum pressure gradient in hood with 1m square openings are larger than in hood with 0.4m square openings.