Experimental and Numerical Investigations on Isolated, Treaded and Rotating Car Wheels

Wheels on passenger vehicles cause about 25% of the aerodynamic drag. The interference of rims and tires in combination with the rotation result in strongly turbulent wake regions with complex flow phenomena. These wake structures interact with the flow around the vehicle. To understand the wake structures of wheels and their impact on the aerodynamic drag of the vehicle, the complexity was reduced by investigating a standalone tire in the wind tunnel. The wake region behind the wheel is investigated via Particle Image Velocimetry (PIV). The average flow field behind the investigated wheels is captured with this method and offers insight into the flow field. The investigation of the wake region allows for the connection of changes in the flow field to the change of tires and rims. Due to increased calculation performance, sophisticated computational fluid dynamics (CFD) simulations can capture detailed geometries like the tire tread and the movement of the rim. Therefore, the wake investigation via PIV is a usable basis to compare it to results of such new CFD simulation methods. In this research, the wind tunnel results are compared to a Delayed Detached Eddy Simulation in OpenFOAM. The rotation of the rim is modeled with a Sliding Mesh and the rotation of the grooves is modeled with a Multiple Reference Frame approach. To investigate correct geometries, the actual tire geometry under rotation is measured to be able to reproduce the experimental setup. The simulation results are compared to the wind tunnel data. The simulations offer further insight into the flow around wheels and their complex wake region.