Sensitivity analysis of the geometrical simplification of an intercity train entering a tunnel

This paper presents a study of several levels of simplification of the geometrical features of the locomotive unit, in good agreement with these proposed in the European standards, in order to study the sensitivity of the compression wave profile and the pressure gradient measured at the tunnel entrance. The European standards permits in computational fluid dynamic studies the simplification of the bogies while other aerodynamically significant features shall be modeled in detail. Here the snowplow, the coupler elements and the bogies are studied to determine the influence of each element on the compression wave and the maximum pressure gradient of a intercity train entering into a tunnel. It is observed that the coupler introduces a delay in the pressure rise measured at the tunnel walls when the train nose is entering. The snowplow introduces a flow detachment that increases the effective cross-sectional area of the train, and so increases the pressure rise. The removal of the bogies clearly modifies the train head cross-sectional area, so its substitution by a dummy box provokes an increase in the pressure rise that approximates the maximum pressure gradient to that obtained from the full-detailed case.