Aerodynamic performance of combined bogie fairings in an 8-car high-speed train

Abstract

Aerodynamic drag accounts for 75%–80% of the total running resistance of high-speed trains operating above 300 km/h, and the bogie region significantly contributes to this drag due to its complex separated flow structures. This study investigates the aerodynamic performance and drag-reduction mechanism of combined bogie fairings applied to a full-scale eight-car high-speed train at 400 km/h using three-dimensional steady Reynolds-averaged Navier–Stokes (RANS) simulations with the k–ω SST turbulence model. Eleven configurations were analyzed, including a baseline model, three single-fairing configurations (side, front, and rear), and seven combined configurations incorporating two to four fairing components, all including the side fairing. Among the single-fairing cases, the side fairing achieved the largest total drag reduction of 7.62% by suppressing flow entrainment into the bogie cavity due to the lateral shielding, while the front fairing yielded a 5.66% reduction mainly through the skin-friction drag reduction. In contrast, the rear fairing increased drag owing to the blockage-induced pressure increase inside the bogie cavity. The optimal combined configuration of Side + Front + Bottom reduced total aerodynamic drag by 18.05% relative to the baseline. This improvement was primarily attributed to a 33.12% decrease in the pressure drag achieved through coordinated control of lateral entrainment, frontal deflection, and upwash suppression into the bogie cavity. Furthermore, adding the rear fairing to the optimal combination showed negligible change in total drag under the forward-running condition, suggesting its potential applicability as a geometrically symmetric configuration for bidirectional operation. The results demonstrate a context-dependent mechanism shift of the front fairing from the skin-friction drag reduction in isolation to the pressure-drag reduction in combination, producing a super-additive interaction. This underscores the importance of integrated bogie flow management for the aerodynamic optimization of high-speed trains.