A fully coupled, 6 degree-of-freedom, aerodynamic and vehicle handling crosswind simulation using the DrivAer model

In a real-world environment, a vehicle on the road is subjected to a range of flow yaw angles, the most severe of which can impact handling and stability. A fully coupled, six degrees-of-freedom CFD and vehicle handling simulation has modelled the complete closed loop system. Varying flow yaw angles are introduced via time dependent boundary conditions and aerodynamic loads predicted, whilst a handling model running simultaneously calculates the resulting vehicle response. Updates to the vehicle position and orientation within the CFD simulation are achieved using the overset grid method. Using this approach, a crosswind simulation that follows the parameters of ISO 12021:2010 (Sensitivity to lateral wind - Open-loop test method using wind generator input), was performed using the fastback variant of the DrivAer model. Fully coupled aerodynamic and vehicle response was compared to that obtained using the simplified quasi-steady and unsteady, one way coupled method. Between the quasi-steady and unsteady simulations, an overshoot in aerodynamic yaw moment for the latter resulted in a larger lateral deviation of approximately 8%. However, the differences in responses between the transient, one-way and fully coupled methods were small for this particular geometry. It is expected that by increasing gust length, differences will appear, as the vehicle is exposed to the larger flow yaw angle for a longer period.