Aerodynamic Simulation of a Parametrically Deformed Rotating Tire

As the automotive industry increasingly shifts toward electrification, reducing vehicle drag becomes crucial for enhancing battery range and meeting consumer expectations. Additionally, recent European regulations require car manufacturers to provide reliable drag data for vehicles as they are configured (WLTP). Vehicle and tire manufacturers can assess tire impacts on vehicle performance through testing. However, to improve designs, it is essential to identify which tire features influence the flow field and overall vehicle performance. Physical tests measure tire behavior under load, but isolating contact patch and tire bulge effects is difficult, as both change together. Simulation allows independent analysis of these factors—something that physical testing alone cannot achieve. This paper investigates the aerodynamic impact of realistic tire deformation parameters—specifically, bulge and contact patch deformations—using Computational Fluid Dynamics (CFD) simulations conducted with PowerFLOW. The standalone tire setup used in this study was validated against experimental results from previous work by Dassault Systèmes. To further assess the impact of these deformations on vehicle drag, simulations were repeated using the generic automotive DrivAer model. Given the complexity of the flow features in a tire wake, the study employed a combination of analysis methodologies, including Principal Component Analysis (PCA) and a vortex tracking algorithm based on the Gamma 2 criterion and single-link hierarchical clustering. The results demonstrate a strong correlation between tire deformation and changes in wake characteristics, which in turn significantly affect the drag coefficient. Two primary flow mechanisms were identified: the flow angles around the contact patch and vortex behavior. While contact patch curvature had a noticeable impact, the most significant drag variations were due to non-linear effects of bulge deformations. A consistent relationship was observed between wake variations generated at the front tires of the DrivAer model and the overall vehicle drag.