Numerical Study On Aerodynamic Effect Of High Speed Train Entering Tunnel

Air flow in a tunnel will be limited by the tunnel’s wall when the train is passing tunnel, this will cause the phenomenon of forming the initial compression waves and pressure wave in the tunnel, as well as import wave phenomenon. As the same time, the aerodynamic load of the high speed train changes with the train entering the tunnel, which will affect the dynamic properties of trains, stability, safety, economy, and ride comfort of drivers and passengers. With the increase of the train speed, the problem about aerodynamics of trains is more attention. So, the paper can make some research about issues.The numerical simulation method is used to simulate the unsteady aerodynamic characteristics of the high speed train CRH3 and CRH380 A. In this way, the distribution of the flow field and the variation of aerodynamic loads are obtained. In solving calculation, the high speed train CRH3 and CRH380 A entering the tunnel models adopted the finite volume method(FVM) and the arbitrary sliding interface(ASI) method which is provided for STAR-CD software. In order to better verify the aerodynamics of the high-speed train entering tunnel, we used the Ahmed Car overtaking on the open wire into the numerical simulation method which is simulated with the train entering tunnel.First, for the simulation of cars open-wire overtaking process, it is established the geometric model of Ahmed cars and the open-wire line model, which can simulate the three dimensional, incompressible and unsteady turbulent air flows around the cars in the open-wire overtaking process. The numerical results are compared with the experimental results and the results of the literature, and the correctness of the numerical simulation method is verified. The numerical simulation focuses on the characteristics of flow field and aerodynamic load in different Reynolds numbers.Second, for simulate the three dimensional, compressible and unsteady turbulent air flows when the train enters a tunnel, we research the characteristics of the initial compression wave and distribution of compression wave in tunnel. The result shows that the initial compression wave with three-dimensional characteristics is that air flow around the train is restricted when the train enters a tunnel, but in the dissemination of a certain distance initial compression wave will become into the one-dimensional plane wave. The magnitude of initial compression wave is proximately proportional to the cube of the train speed. After that, analysis of two types of the high speed train CRH3 and CRH380 A entering the tunnel effect on initial compression wave, the result shows the change of initial compression wave of CRH3 is more severe than that of CRH380 A. For the peak value of the initial compression time of the compression wave, CRH3’s is higher than CRH380A’s.Last, it is analyzed for aerodynamic load variation characteristics when the high-speed train enters tunnel. And the two different trains in different speed conditions of aerodynamic load were compared. The result shows that compression wave enables the drag coefficient increased, expansion wave enables the drag coefficient decreased.It is less affected for lateral force coefficient and the lift coefficient by the compression wave and expansion wave. With the increase of speed, the aerodynamic coefficient and moment coefficient of trains increased. The different aerodynamic forces and moments can cause the lateral vibration of the high speed train.The three-dimensional numerical simulation can effectively show the relation between the pressure fluctuation and aerodynamic load characteristics about the Ahmed car’s overtaking and inside or outside the tunnel when the train is passing. The result of this thesis is useful to give some advice to the pressure fluctuation of the Ahmed car overtaking and inside or outside the tunnel caused by the unbalance of the force and moment which provide some useful reference for the high speed train safety and stable movement.