Aerodynamic performance and dynamic behaviors of a train passing through an elongated hillock region beside a windbreak under crosswinds and corresponding flow mitigation measures

Based on unsteady simulations and decomposed sliding mesh technology, train aerodynamic and dynamic behaviors near an elongated hillock beside a windbreak under a crosswind were analyzed. First, the sudden deterioration of the aerodynamic performance was explained. Then, a mitigation measure was proposed to reduce the impact of the elongated hillock on the train. Finally, the dynamic responses for the original elongated hillock and mitigation measure were compared. The results showed that two symmetric vortices along the railway were generated by the elongated hillock, and in the position between these two vortices, a strong wind speed occurred, which resulted in a sudden impact on the train, and the aerodynamic impacts were the largest on the head car. A certain distance from the elongated hillock to the windbreak could make a mitigation effect. For the original elongated hillock, there was a severe yawing phenomenon of more than 83 mm/3° from the centerline of the car body for the head car. For the mitigation measure, the safety index and vibration displacement of the head car and tail car decreased effectively.