Effects of embankment layouts on train aerodynamics in a wind tunnel configuration

Crosswind stability of rolling stocks running on an embankment has been a key focus for decades, stemmed from the high overturning risks under crosswind. The correct reproduction of the embankment layout in a wind tunnel is therefore of great significance for estimating the train's aerodynamics and running safety. In this study, four different 6-m-high embankment layouts are proposed to replicate realistic wind tunnel configurations with the improved detached eddy simulation (IDDES) method. These helped to estimate the aerodynamics of a leading vehicle when subjected to a block wind profile of 45 m/s at the typical yaw angle of 30 degrees. Furthermore, a static wind tunnel test with a 1:20 scaled train/embankment model enabled the validation of the numerical algorithm. The overall results indicate that all the aerodynamic coefficients of the leading vehicle mounted on the leeward track of the embankment top, decrease rapidly with the extending length of the upstream embankment. Similar aerodynamic performance appears on scenarios such as wall-to-wall (W2W) and partially wall-to-wall (P-W2W), which highlight equivalences between W2W and P-W2W under yaw effects. However, those particular scenarios considerably underestimate the aerodynamic coefficients compared with a more realistic scenario based on open domain (OD) and motion boundaries. Therefore, the conservative assessment of the vehicle aerodynamic characteristics based on the finite-length-embankment in a wind tunnel test could be taken into consideration for determining the running safety.