Purdue University Graduate School
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posted on 2021-08-11, 19:01 authored by ROTEM LIVNYROTEM LIVNY
The development work of a race car revolves around numerous goals such as drag reduction,
maximizing downforce and side force, and maintaining balance. Commonly, these goals
are to be met at the same time thus increasing the level of difficulty to achieve them. The
methods for data acquisitions available to a race team during the season is mostly limited to
wind tunnel testing and computational fluid dynamics, both of which are being heavily regulated
by sanctioning bodies. While these methods enable data collection on a regular basis
with repeat-ability they are still only a simulation, and as such they come with some margin
of error due to a number of factors. A significant factor for correlation error is the effect of
tires on the flow field around the vehicle. This error is a product of a number of deficiencies
in the simulations such as inability to capture loaded radius, contact patch deformation in
Y direction, sidewall deformation and overall shifts in tire dimensions. These deficiencies
are evident in most WT testing yet can be captured in CFD. It is unknown just how much
they do affect the aerodynamics performance of the car. That aside, it is very difficult to
correlate those findings as most correlation work is done at WT which has been said to be
insufficient with regards to tire effect modeling. Some work had been published on the effect
of tire deformation on race car aerodynamics, showing a large contribution to performance
as the wake from the front tires moves downstream to interact with body components. Yet
the work done so far focuses mostly on open wheel race cars where the tire and wheel assembly
is completely exposed in all directions, suggesting a large effect on aerodynamics.
This study bridges the gap between understanding the effects of tire deformation on race car
aerodynamics on open wheel race cars and closed wheel race cars. The vehicle in question
is a hybrid of the two, exhibiting flow features that are common to closed wheel race cars
due to each tire being fully enclosed from front and top. At the same time the vehicle is
presenting the downstream wake effect similar to the one in open wheel race cars as the
rear of the wheelhouse is open. This is done by introducing a deformable tire model using
FEA commercial code. A methodology for quick and accurate model generation is presented
to properly represent true tire dimensions, contact patch size and shape, and deformed dimension,
all while maintaining design flexibility as the model allows for different inflation
pressures to be simulated. A file system is offered to produce CFD watertight STL files that
can easily be imported to a CFD analysis, while the analysis itself presents the forces and
flow structures effected by incorporating tire deformation to the model. An inflation pressure
sweep is added to the study in order to evaluate the influence of tire stiffness on deformation
and how this results in aerodynamic gain or loss. A comparison between wind tunnel
correlation domain to a curved domain is done to describe the sensitivity each domain has
with regards to tire deformation, as each of them provides a different approach to simulating
a cornering condition. The Study suggests introducing tire deformation has a substantial
effect on the flow field increasing both drag and downforce.In addition, flow patterns are
revealed that can be capitalized by designing for specific cornering condition tire geometry.
A deformed tire model offers more stable results under curved and yawed flow. Moreover,
the curved domain presents a completely different side force value for both deformed and
rigid tires with some downforce distribution sensitivity due to inflation pressure.


Degree Type

  • Master of Science in Engineering


  • Engineering Technology

Campus location

  • Indianapolis

Advisor/Supervisor/Committee Chair

Hamid Dalir

Additional Committee Member 2

Andy Borme

Additional Committee Member 3

Chris Finch