The effect of tires on the overall aerodynamic drag in a car-tire assembly has been studied and deemed considerable from past studies. It has been shown that it is important to understand how the vehicle body and the tires influence the flow structures generated. Previous studies focused on the tire attributes that have an impact on the aerodynamic performance of the vehicle. These tire attributes, however, have not been studied to the extent where one can get a better understanding of the impact of each of these attributes. This paper studies the impact that specific tire attributes have on the overall aerodynamic drag on the vehicle. A thorough and systematic sensitivity study of the effect of tire attributes of a standalone tire was performed to better understand the flow structures around the car body and the improvement in the aerodynamic performance of the vehicle.
In this study, the DrivAer model is used due to the extensive research that has been done on the model. A baseline CFD model of the tire-vehicle assembly of the DrivAer model is simulated using Ansys FLUENT in the open road domain to understand the flow structures around the body of the vehicle. Simulations are done on the fastback configuration of the DrivAer model. A smooth underbody is chosen for this simulation in order to avoid complexities in the meshing. A cuboid shaped open road domain is created, keeping in mind the blocking ratio that is adequate to emulate the flow around the vehicle under open road conditions. Ground simulation and rotating wheel boundary conditions are used to simulate the vehicle moving on the road. The contribution of the tire towards the aerodynamic drag on the vehicle is studied. Coefficient of Drag and coefficient of pressure results from the simulation are validated from experimental data. This is used to create a simulation procedure with appropriate meshing techniques and solution methods in order to simulate for the baseline tire-vehicle assembly and the optimized tire-vehicle assembly. Data from these simulations are used to quantitatively compare the drag contribution of different parameters of the tires.
The sensitivity analysis of the tire-vehicle assembly model performed gives a better insight into the modelling techniques that can be used on a car-tire assembly, as well as the impact of the parameters that could be selected for future tire model optimization.