Numerical simulation and comparison of the slipstreams of trains with different nose lengths under crosswind

Abstract

The slipstreams induced by high-speed trains under crosswind are studied in this paper by the detached-eddy simulation (DES) method. First, the formation and development of the slipstream induced by a train (5 cars) with a 4 m nose length are analysed in detail, including at different heights and widths on the windward side (WWS) and leeward side (LWS). Then, the slipstreams with and without crosswind are compared, and the differences are presented. Finally, by considering four different nose lengths (4, 7, 9, and 12 m) under crosswind, the differences in the slipstreams induced by different nose lengths are given and analysed. The results show that on the WWS at z = 0.5 m above the top of the rail (TOR), the slipstream velocity coefficient ‘U’ decreases at the position of the nose due to a velocity cancellation and stagnation effect. On the LWS, from D = 0 m–145 m, where ‘D’ represents the distance from the nose point, at y = 1.9 m and 2.15 m beside the centre of rail (COR), there are two peak values at the position of the nose caused by the impact of the nose point and the strong disturbance of the bogie area. At y = 2.65 m and 3.65 m, the change in U is relatively complex due to the effect of vortexes on the LWS. The effect of crosswind on the slipstream velocity is different in different regions around the train. In the region close to the train side and the bottom, the value of U on the WWS is the smallest, followed by that in the no wind case, and that on the LWS is the largest. In other regions, the values of U on the WWS and LWS are larger than that in the no wind case. For different nose lengths, on the WWS, the change in U is smoother with increasing nose length due to more stable flow around the nose. On the LWS, the change in U with increasing nose length is relatively clear only at the positions around the nose of the head car and tail car. In the regions along the middle cars, the U values for trains with different nose lengths change with the same trends and vary intertwined.