Aerodynamic Interference Mechanism of Moving Vehicles on a Bridge Deck in Crosswind Environment

Abstract

Super long-span bridges offer great convenience, but, because of their high decks, they also suffer from traffic safety problems related to strong winds. In this paper, large eddy simulation and dynamic mesh techniques for computational fluid dynamics are used to explore the aerodynamic forces acting on vehicles travelling on bridges and the mechanism of the aerodynamic interference between two vehicles during the processes of overtaking (from the same direction) and approaching (from opposite directions). The results indicate that during overtaking or approaching, the lateral aerodynamic interference between moving vehicles in a crosswind exhibits several characteristics that are fundamentally different from those of the interference between static vehicles. In the area behind a moving vehicle, a pressure cavity (a low-pressure zone) exerts a suction effect on the crosswind, which causes the crosswind in this region to change direction. This suction effect will markedly influence the aerodynamic force on another vehicle travelling in an adjacent lane in a crosswind, even when the latter vehicle is not directly sheltered by the former. The ratio of the velocities of the overtaking and overtaken vehicles exerts a significant influence on the aerodynamic forces that act on vehicles in a crosswind, and the transverse interval exerts a significant influence on the aerodynamic forces on both the windward and leeward vehicles. These lateral aerodynamic interferences cause vibrations of the vehicle and oscillations of the vehicle’s contact forces with the bridge deck or road, which threaten its driving safety and comfort in a crosswind.