Coupled analysis of unsteady aerodynamics and vehicle motion of a road vehicle in windy conditions

The two-way coupling of full-scale vehicle motion and the surrounding turbulence motion has been realized on a developed unsteady aerodynamic simulator for a road vehicle. A large-eddy simulation (LES) technique has been applied to reproduce the unsteady turbulence motion, and an unstructured finite volume method has been adopted to explain the complicated geometry of a full-scale road vehicle. Three-degree-of-freedom equations of the vehicle’s dynamic motion are incorporated into the developed LES code, and the motion is numerically reproduced by coupling the arbitrary Lagrangian–Eulerian (ALE) method and Navier–Stokes equations in a non-inertial reference frame. The simulation code is implemented on a massively parallel processor to meet the demands of the large-scale, long-term aerodynamic simulations of full-scale road vehicles. As a typical application of the coupled analysis, an unsteady aerodynamics simulation of a simplified heavy-duty truck in windy conditions is demonstrated, and the effects of the unsteady aerodynamics on the truck’s motion are investigated. The obtained results are compared with the results of a conventional quasi-steady analysis, and certain differences in the vehicle path and the yaw angle are identified. The effects of the transitional aerodynamics on variables related to driver’s perception are significant. These results clearly indicate the importance of estimating the unsteady aerodynamic forces in a vehicle motion analysis.