COMPUTATIONAL FLUID DYNAMICS SIMULATION AND STABILITY ANALYSIS OF VEHICLE ON BRIDGE UNDER STRONG WINDS

Abstract

 This paper describes an investigation on vehicle stability when crossing a bridge under strong wind by Computational Fluid Dynamics (CFD) and vehicle dynamics stability model. Large Eddy Simulation (LES) was implemented in the CFD to compute time-histories of vehicle’s aerodynamic force coefficients when moving on the bridge at different traffic lanes. The aerodynamic force coefficients were later utilized to compute wind loads on the vehicle, based on which vibration and stability of vehicle were evaluated using vehicle dynamics model. Simulation results show that the flow fields around vehicle vary for each traffic lane and they were strongly influenced by the shear layer separated from leading edge of the bridge girder. As a result, the aerodynamic characteristics acting on the vehicle and the normal force on each wheel vary according to the traffic lane. Critical conditions of vehicle instability are defined as overturning and sideslip or yawing. The critical wind speed associated with each condition is defined as the wind speed that causes the normal force on one of the wheels becomes zero. Analyses demonstrate that the lowest critical wind speed occurs when the vehicle moves on the windward lane and it increases toward the leeward lanes. It is also observed that at any lanes, the critical condition for yawing instability occurs at a lower wind speed than the critical condition for overturning instability.