Analysis of the aerodynamic effects of different nose lengths on two trains intersecting in a tunnel at 350Â km/h

The three-dimensional compressible Navier-Stokes equation and k-ε turbulence model are used to simulate the flow and pressure waves caused by two trains passing each other in a tunnel. The simulation results were verified by comparison with the results of a full-scale experiment. This simulation results indicate that the positive peak of the initial compression wave on the tunnel wall has a logarithmically decreasing trend with increasing nose length. This tendency is more obvious near the tunnel portal than in the tunnel, and the positive peak caused by a train with a nose length of 12 m at a distance of 20 m from the tunnel entrance is 10.26% less than that caused by a train with a nose length of 4 m. Throughout the intersection process, the peak-to-peak amplitude of body surface pressure decreases with increasing longitudinal distance from the front nose tip. The influence of different nose lengths on the surface pressure on the train body is mainly concentrated at the front and rear of the train. The fluctuation amplitude of the surface pressure on the head car with a 4 m nose is 1.63 times that of a head car with a 12 m nose. The amplitudes of the lateral force and overturning moment are also influenced by the nose length, with the strongest effect on the head car and a stronger effect on the middle car than on the tail car. A shorter train nose results in a more significant influence on the train total drag. As the nose length changes from 4 m to 7 m, the maximum total drag decreases by 6.71%; however, as the nose length changes from 9 m to 12 m, the maximum total drag decreases by only 0.16%.