The importance of unsteady aerodynamics to road vehicle dynamics

• New driver model to react to yawed aerodynamic inputs.
• Simulated driver reaction to unsteady lateral aerodynamics of a road vehicle.
• Two different onset wind cases and 5 sources of aerodynamic unsteadiness.
• Unsteady onset flow dominates vehicle handling, greater unsteadiness is a refinement concern.

This paper investigates the influence that different unsteady aerodynamic components have on a vehicle's handling. A simulated driver and vehicle are subject to two time-dependent crosswinds, one representative of a windy day and the second an extreme crosswind gust. Initially a quasi-static response is considered and then 5 additional sources of aerodynamic unsteadiness, based on experimental results, are added to the model.From the simulated vehicle and driver, the responses are used to produce results based on lateral deviation, driver steering inputs and also to create a ‘subjective’ handling rating. These results show that the largest effects are due to the relatively low frequency, time-dependent wind inputs. The additional sources of simulated unsteadiness have much smaller effect on the overall system and would be experienced as increased wind noise and reduced refinement rather than a worsening of the vehicle's handling.