Study On Train-tunnel Aerodynamic Effect Characteristics Of Cross Passages At The Entrance Of The Tunnel

With the improvement of the construction of the high-speed railway network in the eastern region of China,the country began to vigorously build high-spee d railway lines in the central and western regions.The central and western regio ns of China have complicated terrains and many mountain valleys and the routes are mostly bridge and tunnel sections.In order to solve the problem of the aer odynamic effect of the train-tunnel in the bridge-tunnel connection section,this p aper puts forward measures to build a decompression channel at the tunnel shall ow buried section to relieve the aerodynamic effect generated by the train enteri ng the tunnel and carry out research.The method of combining theoretical analy sis,dynamic model test and numerical simulation was used to study the aerodyn amic effect of the train-tunnel after the decompression channel was installed.Bas ed on the FLUENT calculation software,various model conditions are established for the characteristics of the decompression channel,and the impact of the deco mpression channel on the mitigation effect of the aerodynamic effect of the train-tunnel is studied from the length,area,position and number of the decompress ion channel.In addition,this paper also studies the effect of the train on the rel ief effect of the decompression channel at different speed levels and when the tr ain meets at different positions in the tunnel.The main research contents and co nclusions are as follows:(1)A three-dimensional viscous and compressible unequal-entropy unsteady flow numerical calculation model was established,and the numerical simulation c alculation results and dynamic model test results were compared with each other to verify that the pressure values obtained at the measuring points were basically consistent,thus illustrating the accuracy of the research method.(2)Through the study of the pressure relief principle of the decompression channel,it was found that the decompression channel can play a diversion role,thereby significantly reducing the pressure value of the tunnel entrance section;The upward trend reduces the pressure gradient value in the back section of the tunnel and the magnitude of the micro-pressure wave at the exit of the tunnel.(3)Through the study of the influence of the characteristics of the decomp ression channel on the pressure relief effect,in the calculation conditions in this paper,the length of the decompression channel is 10m(small length),40m from the opening(far away from the opening),and the area is 20-25m~2 When the nu mber is 2,it has the best mitigation effect on the aerodynamic effect of the car tunnel.(4)Through the study of the speed of the train and the effect of the train rendezvous on the pressure relief effect of the decompression channel,it is fou nd that the decompression channel does not change the pressure reduction effect of the micro pressure wave at the entrance when the train speed changes;The most unfavorable situation occurs when the same type of pressure wave is superi mposed in the tunnel.