Influence of incoming turbulence on aerodynamic forces of a high-speed train

The influence of incoming turbulence on the aerodynamics of a high-speed train is numerically investigated using the Improved Delayed Detached Eddy Simulation (IDDES) combined with Synthetic Turbulence Generation (STG). The results reveal that increasing turbulence intensity significantly enhances the drag and lift coefficients of the train, with the rate of increase amplifying as the turbulence length scale grows. The incoming turbulence induces effects analogous to crosswind conditions, weakening the aerodynamic impact on the head carriage while accelerating airflow around the curved sections of the tail carriage. Moreover, the turbulent kinetic energy within the shear layers adjacent to the bogie cavity increases with turbulence intensity, facilitating enhanced flow ingress into the cavity and intensifying interactions with the bogie and cavity structures, thereby augmenting both drag and lift. Additionally, the presence of incoming turbulence produces a thinner boundary layer, characterized by a reduced shape factor and elevated viscous drag. Specifically, higher turbulence intensity leads to a smaller shape factor and a steeper velocity gradient, thereby increasing viscous drag. In contrast, larger turbulence length scales exhibit the opposite trend, manifesting as a decrease in viscous drag.