Investigation of the Effect of Tire Deformation on Open-Wheel Aerodynamics

This paper introduces a finite element (FE) approach to determine tire deformation and its effect on open-wheeled racecar aerodynamics. In recent literature tire deformation was measured optically. Combined loads like accelerating at corner exit are difficult to reproduce in wind tunnels and requires several optical devices to measure the tire deformation. In contrast, an FE approach is capable of determining the tire deformation in combined load states accurately. The FE tire model was validated using computer tomography images, 3D scan measurements, contact patch measurements and stiffness measurements. The deformed shape of the FE model was used in a computational fluid dynamics (CFD) simulation. A sensitivity study was created to determine the effect of the tire deformation on aerodynamics for unloaded and loaded tires. In addition, the influence of these tire deformations was investigated in a CFD study using a full vehicle model. The CFD model was validated through full scale wind tunnel tests as well as on-road tests. Finally, a straight-line and a steady state cornering maneuver based on a vehicle dynamics simulation were simulated using this combined approach of FE and CFD. The tire deformation included proper wheel load, wheel speed and slip angle for each wheel. The CFD full vehicle model took chassis slip angle, body roll angle and wheel steering angle into account in order to match the real driving situation. The results show that realistic tire deformations provide better insight into the effect of rotating wheels on aerodynamics of full vehicles, especially that of race cars.