Coupled Analysis of Unsteady Aerodynamics and 6DoF Motion of a Heavy Duty Truck in Strong Wind Gusts

Abstract

In this study, a one-way coupled simulation of unsteady aerodynamics and vehicle dynamics has been applied to a heavy duty truck subject to a sudden crosswind. Transient aerodynamic forces and moments were predicted by a large-eddy simulation (LES) technique assuming that the truck was in a straight running with fixed attitude. In the numerical result, overshooting profiles of aerodynamic forces and moments were observed. Then, they were input to a vehicle dynamics simulation for the coupled analysis. In order to investigate bouncing, pitching and rolling motions of the vehicle, the vehicle dynamics simulation method has been extended to the six degrees of freedom (6DOF) motion. The result indicated that the vertical motions could change a clearance under the truck’s body significantly. The numerical results were compared with a vehicle dynamics simulation with three degrees of freedom (3DOF) in the horizontal directions. The yaw rate, which strongly relates to driver’s feeling of stability, showed quantitatively different behaviors though the trajectory of the truck was almost similar to each other simulation. The effect of transient aerodynamic forces and moments were also discussed. Additional vehicle dynamics simulation based on a quasi-steady aerodynamics assumption was conducted and the result was also compared with the coupled simulation. Effect of the transient aerodynamic forces and moments, which appeared only in the one-way coupled simulation were clarified for the vehicle motions in all directions.