Numerical investigation on the aerodynamic characteristics of high-speed train under turbulent crosswind

Increasing velocity combined with decreasing mass of modern high-speed trains poses a question about the influence of strong crosswinds on its aerodynamics. Strong crosswinds may affect the running stability of highspeed trains via the amplified aerodynamic forces and moments. In this study, a simulation of turbulent crosswind flows over the leading and end cars of ICE-2 high-speed train was performed at different yaw angles in static and moving ground case scenarios. Since the train aerodynamic problems are closely associated with the flows occurring around train, the flow around the train was considered as incompressible and was obtained by solving the incompressible form of the unsteady Reynolds-averaged NavierStokes (RANS) equations combined with the realizable k-epsilon turbulence model. Important aerodynamic coefficients such as the side force and rolling moment coefficients were calculated for yaw angles ranging from -30 degrees to 60 degrees and compared with the results obtained from wind tunnel test. The dependence of the flow structure on yaw angle was also presented. The nature of the flow field and its structure depicted by contours of velocity magnitude and streamline patterns along the train's cross-section were presented for different yaw angles. In addition, the pressure coefficient around the circumference of the train at different locations along its length was computed for yaw angles of 30 degrees and 60 degrees. The computed aerodynamic coefficient outcomes using the realizable k-epsilon turbulence model were in good agreement with the wind tunnel data. Both the side force coefficient and rolling moment coefficients increase steadily with yaw angle till about 50 degrees before starting to exhibit an asymptotic behavior. Contours of velocity magnitude were also computed at different crosssections of the train along its length for different yaw angles. The result showed that magnitude of rotating vortex in the lee ward side increased with increasing yaw angle, which leads to the creation of a low-pressure region in the lee ward side of the train causing high side force and roll moment. Generally, this study shows that unsteady CFDRANS methods combined with an appropriate turbulence model can present an important means of assessing the crucial aerodynamic forces and moments of a high-speed train under strong crosswind conditions.