Numerical study on the contribution of local flow to aerodynamic drag for high-speed trains

Artikel i vetenskaplig tidskrift, 2025

Surface-based aerodynamic drag breakdown encounters limitations in explaining subtle drag-reduction schemes for modern high-speed trains. In this study, delayed detached eddy simulation (DDES) is employed to conduct a control volume analysis of turbulent losses around an eight-car train, quantifying the contributions of turbulence production and viscous dissipation to aerodynamic drag in specific local flow regions. While the component contributions identified by the volumetric approach largely align with surface-based breakdown results, the volumetric method offers more detailed spatial insights. For instance, the bogie region contributes the most to aerodynamic drag, accounting for 39%, with volumetric losses concentrated along the sides and underneath the bogies. This result supports the effectiveness of bogie skirt and belly fairing applications. Furthermore, the volumetric analysis reveals that viscous dissipation losses in the upper body region are primarily due to wall friction, whereas in the lower body region, turbulent viscosity from separated shear layers dominates. In the wake region, turbulence and outflow flux contribute approximately 15% of the total drag, indicating substantial potential for aerodynamic optimization. The detailed identification of local region contributions provided in this study offers a complementary perspective that can inform the design and optimization of future high-speed train.