TIRE DEFORMATION MODELING AND EFFECT ON AERODYNAMIC PERFORMANCE OF A P2 RACE CAR
Creators: name: LIVNY, ROTEM
Publisher: name: Purdue University Graduate School
Year: 2021
Subjects: Aerodynamics (excl. hypersonic aerodynamics)
Automotive engineering not elsewhere classified

description: 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 goalsare to be met at the same time thus increasing the level of difficulty to achieve them. Themethods for data acquisitions available to a race team during the season is mostly limited towind tunnel testing and computational fluid dynamics, both of which are being heavily regulatedby sanctioning bodies. While these methods enable data collection on a regular basiswith repeat-ability they are still only a simulation, and as such they come with some marginof error due to a number of factors. A significant factor for correlation error is the effect oftires on the flow field around the vehicle. This error is a product of a number of deficienciesin the simulations such as inability to capture loaded radius, contact patch deformation inY direction, sidewall deformation and overall shifts in tire dimensions. These deficienciesare evident in most WT testing yet can be captured in CFD. It is unknown just how muchthey do affect the aerodynamics performance of the car. That aside, it is very difficult tocorrelate those findings as most correlation work is done at WT which has been said to beinsufficient with regards to tire effect modeling. Some work had been published on the effectof tire deformation on race car aerodynamics, showing a large contribution to performanceas the wake from the front tires moves downstream to interact with body components. Yetthe work done so far focuses mostly on open wheel race cars where the tire and wheel assemblyis 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 caraerodynamics on open wheel race cars and closed wheel race cars. The vehicle in questionis a hybrid of the two, exhibiting flow features that are common to closed wheel race carsdue to each tire being fully enclosed from front and top. At the same time the vehicle ispresenting the downstream wake effect similar to the one in open wheel race cars as therear of the wheelhouse is open. This is done by introducing a deformable tire model usingFEA commercial code. A methodology for quick and accurate model generation is presentedto properly represent true tire dimensions, contact patch size and shape, and deformed dimension,all while maintaining design flexibility as the model allows for different inflationpressures to be simulated. A file system is offered to produce CFD watertight STL files thatcan easily be imported to a CFD analysis, while the analysis itself presents the forces andflow structures effected by incorporating tire deformation to the model. An inflation pressuresweep is added to the study in order to evaluate the influence of tire stiffness on deformationand how this results in aerodynamic gain or loss. A comparison between wind tunnelcorrelation domain to a curved domain is done to describe the sensitivity each domain haswith regards to tire deformation, as each of them provides a different approach to simulatinga cornering condition. The Study suggests introducing tire deformation has a substantialeffect on the flow field increasing both drag and downforce.In addition, flow patterns arerevealed 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 andrigid tires with some downforce distribution sensitivity due to inflation pressure.