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 tire and car manufacturers to provide reliable drag data.
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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 tire and car manufacturers to provide reliable drag data. A significant factor influencing vehicle drag is the highly turbulent wake generated by rotating tires. Accurate correlation between wind tunnel experiments and numerical simulations is essential, yet discrepancies often arise due to the dynamic behavior and technical challenges in measuring tire deformation, leading to inconsistencies between tire deformations observed in wind tunnels and those modelled in simulations.
This Master’s Thesis 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 deformation parameter tests are carried out in a standalone tire setup, which is validated from previous work by Dassault Systèmes and experimental results. To further assess the impact of these deformations on vehicle drag, the tests were repeated using the DrivAer model, an IP free model provided by the Technical University of Munich. Given the complexity of the flow features in a tire wake, the analysis of the results consisted of two different approaches: a statistical approach based on Principal Component Analysis (PCA), and a vortex behaviour and wake development analysis, including a vortex tracking algorithm based on the Gamma 2-Criterion and single-link hierarchical clustering.
The results identify the most influential deformation parameters based on their impact on the drag coefficient and the wake behaviour changes. Two primary wake development behaviours were identified: wake contraction and wake expansion. An analysis of the transient flow showed how these two trends resulted from changes in the unsteady behaviour introduced by certain deformation parameters. The relevance of these wake development changes was portrayed by the impact of certain deformations on the full vehicle drag as a result of
complex wake interactions.
