Differences in aerodynamic effects when trains with different marshalling forms and lengths enter a tunnel

Unsteady Reynolds-averaged Navier-Stokes (URANS) simulations were performed to simulate trains with different marshalling forms and lengths entering a tunnel. Three models, including a short train, a double train and a long train, were used to analyse the influence of the train configuration on the pressure variations during a train's passage. The results of the numerical predictions were validated against existing experimental data, with which they showed good agreement. The differences in the maximum pressure peak distribution and the pressure fluctuations were analysed by means of Mach diagrams. The results show that the grouping length exerts a considerable influence on the amplitude of the pressure on the train body and that the influence of the grouping length on the pressure variation on the tunnel wall varies with the location in the tunnel. The tunnel space can be divided into three and four zones with regard to the influences on the maximum positive and negative pressure values, respectively. The different marshalling forms also influence the maximum peak values and local profiles of the pressure history curves, although this influence is much slighter than that of the train's grouping length.