الفهرس 
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Abstract
The aim of the thesis is to characterize the aerodynamic performance of a rotating wheel fitted with different tyre features in an isolation condition; Slick Tyre (ST) as the reference case; Treaded Tyre (TT); and Non-pneumatic tyre (NPT). A three-dimensional wheel model, rotating in complete contact with the ground, was implemented for the experimental part. The experimental forces, moments, and pressure measurements were time-averaged to analyze the aerodynamic performance of the three different wheel types and verify the adopted numerical model. Further numerical investigations focused on exhibiting the wake structure at the wheel’s downstream region, inherently unsteadiness effects, have also been studied. For the TT wheel, the change in the lateral groove width and depth was examined for three-different off-road tyre categories; Soft TT, Hard TT, and Ultimate TT. Besides, the lateral groove V-angle (ꝋ) of the TT wheel was also tested in the present work, while only increasing the number of spokes for the NPT wheel case was considered.
Compared to the ST wheel, the TT wheel pressure measurements exhibit a remarkable higher base-pressure at the wheel back, caused by the earlier wheel top-separation, which led to a significant drag reduction by 5.2%. Besides, the measured TT wheel lift is also reduced by around 11.7%. On the other hand, the measured moment coefficient significantly raised, by about 181.8% compared to the ST wheel. The increase in the lateral grooves V-angle (ꝋ) has an improving influence on the tread block shape, where lower drag and moment coefficients were experimentally obtained by around 12% and 37.5% at ꝋ=60º, respectively. In addition, increasing V-angle (ꝋ), produced thinner boundary layer with fewer separation bubbles, resulting in a maximum of 4.5% rise in the lift at ꝋ=60º. The increase in the lateral groove width and depth simultaneously dramatically increases the drag by a maximum of 13% at ꝋ=0º when stepping from W (3-3) to W (4-4) and from W (4-4) to W (5-5), respectively. The lift coefficient is steeply depressed by a maximum of 10% and 33% at ꝋ=15º, when moving from W (3-3) to W (4-4) and from W (4-4) to W (5-5), respectively. On the other hand, the moment coefficient has a dramatic stepped rise while widening the lateral groove width by an average of around 40% for each step.
For the NPT wheel, a similar flow pattern and physics to the ST wheel were reported through the measurements since they have the same smooth tread. However, the spoke side profile showed a predominant side flow variation, which led to a 14% and 20% increase in the NPT wheel drag and lift coefficient measurements, respectively. The effect of increasing the number of spokes in the experiments showed an exponential decrease in the drag, lift, and negative moment coefficients by about 6%, 3%, and 8%, respectively.
In general, the comparison between the present ST wheel computational and experimental outcomes mostly showed that ANSYS Fluent software largely exhibits reasonable flow physics. Furthermore, using URANS could exceptionally provide the best matching results for the wheel studies. Utilizing the 2-equation k-ω SST turbulence model seemed to be the most accurate model among the various turbulence models, notably in the transient form. The poorly known top wheel separation is clearly identified by the present computational work and was follows the M-R-S separation criterion