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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%. [ABSTRACT FROM AUTHOR]

Abstract: An obvious pressure change and a micro-pressure wave are generated when a train enters a tunnel at high-speed, which impacts on the comfort of passengers and the environment around the tunnel. Thus, it is necessary to study the aerodynamics of tunnels in order to reduce the pressure change and micro-pressure wave. Our laboratory owns an advanced moving-model device that can simulate two trains crossing in the open air or trains entering a tunnel, with a maximum speed of 400km/h. This paper studies the pressure change, the micro-pressure wave and a series of hoods using three-dimensional numerical simulations and moving-model experiments. From a comparative study, we obtain rules governing the influence of hoods on the micro-pressure wave, and reasonable shapes and parameters of hoods are designed. [Copyright &y& Elsevier]