Research On The Aerodynamic Effect Of High-speed Trains CRH380A With Inter-Car Cap Passing Each Other Through A Tunnel

With the increasing of the train speed, the related aerodynamic problems become moreand more notable. Because of the compressibility of air and the limited flowing space,aerodynamic phenomena such as pressure waves, micro-pressure waves,entry/exit waves andlateral vibration will be generated inside or outside the tunnel when the high-speed trainpassing through it. The tunnel pressure waves can propagate into trains and then cause theaural discomfort problems such as tinnitus, eardrum hurts etc. What’s more, the tempestuouspressure fluctuations may deteriorate safety of train running in the tunnel. Especially, twohigh-speed trains passing by each other in the tunnel, the transient pressure changes is evenmore violent than that a single train passes a tunnel which leads to more serious and morecomplicated aerodynamics in transient, air force and so on. Therefore, it is extremelynecessary to do the profound and comprehensive aerodynamics research of two high-speedtrains passing through in tunnel.When a high-speed train passes each other through a tunnel, the air flow around it is innature unsteady, compressible, turbulent, three-dimensional with a high Reynolds number,Soit is a challenge for numerical simulation study of high-speed train through the tunnel in thecomputational domain, numerical methods, computational resources. In the paper, based onthe three-dimension unsteady N Sequation of compressible viscous fluid and theSST k high Reynolds turbulent model, pressure and aerodynamics forces variationinduced by two high-speed trains passing through in tunnel were calculated numerically bymeans of the fiinite volume method. To avoid the unreasonable physical phenomena innumerical simulation, a smooth start method that permits the train to accelerate graduallyfrom stationary to full speed was adopted. PISO algorithm was used to solve the Reynoldsaveraged equations, and MARS scheme was used to discretize the convective term. Theresulted algebraic equations were solved by using the AMG method, and the reasonable initialand boundary conditions were implemented.Due to the lack of experimental data, the tunnel pressure waves were taken as benchmarkdata, comparison studies were performed with one-dimensional flow model numericalsimulation when the train passing the tunnel, to verify the validity of the numerical method.Based on all above work, the characteristics of flow field were analyzed in detail during theCRH380A passes each other through a tunnel, and the formation mechanism of the pressurewaves and lateral vibration were explained from the three-dimension unsteady property of theturbulent flow. Finally, we use three wall boundary functions to analyze the aerodynamic oftrain passing a tunnel respectively. They are standard wall boundary approach method,un-equilibrium wall boundary approach method and low Reynolds number hybrid wall boundary approach method to deal with CRH380A high-speed trains with different wallfunctions at one third of the tunnel when two trains passing through each other with samevelocity to comparison analysis. The results shows that there are almost the same tendency ofthe surface pressure distribution,aerodynamic forces and moments, and they have the sameamplitude value of variation when high-speed trains meeting at one third of the tunnel whenthey passing through each other with same velocity. The research method and conclusion ofthis paper can provide a beneficial reference for the further parameters study.