Numerical Simulation of Air Flow Properties around High Speed Train in Very Long Tunnel
Numerical simulation of air flow disturbed around a train body with different angle of train nose and different velocity of high speed train in a very long tunnel have been made. Three-dimensional flow theory is capable of modeling the effects of interest in the tunnel environment. The scale of train is 2500mm×320mm×427mm length×width×heigh, and the scale of tunnel is 150m×10.4m×8.2m length×width×heigh. Train speed is 432km/h, 500km/h and 600km/h respectively. The distributions of pressure, velocities streamline and second flow around high speed train in a very long tunnel space can be obtained by simulating. Results show that the train nose angles and train speed affects the air flow around the train strongly. The pressure drag increases with rising of the nose angles and train speed, and it reaches to the highest value of 23073 Pa when the angle is 60 0 and 32466Pa as the velocity is 600km/h. The air velocity in the annular space is quite enormous and the maximize value is 178m/s with train nose 60 0 and 247m/s with train speed 600km/h. The simulation results can be taken to help us for study the high-speed train energy-consuming, maximum velocity, safety and stabilization when it running in a very long tunnel.
Description of the flow equations around a high speed train inside a tunnel
Abstract The present article focuses on the analysis of the equations that describe the flow when a high speed train enters a tunnel. The disparity in time and length scales allows the problem to be decomposed in different regions and regimes when matched appropriately produce the full description of the flow. The aforementioned regions are the flow upstream and downstream of the train, the areas near the nose and tail of the train, and the flow in the gap between the train and the tunnel. The regimes are analysed based on the flow regions, time scales, length scales and velocity scales. All those regions and regimes are conveniently formulated and the flow key scales are analysed and described, which allows for a simplified and robust formulation. The aforementioned formulation is implemented in a computational program that needs some external coefficients, namely the pressure signature of the train, that should be obtained only once and it could be derived from experimental data or CFD. Comparison with experimental and numerical data from other references are provided. Finally, the thermal problem is briefly introduced and some comments on the tunnel cooling problem are considered.
Laminar heat or mass transfer in rectangular channels and in cylindrical tubes for fully developed flow: comparison of solutions obtained for various boundary conditions
Abstract A comparison is made of results obtained with various boundary conditions at the wall of the channels. By comparing blood Sherwood numbers for finite wall resistance with those for constant concentration boundary condition only a small variation is found for various points along the blood channel.