Wheel rim tyre CFD modelling

Abstract

In this thesis, the flow around an isolated wheel at Re = 5:3 105 is investigated for different rotation modelling techniques and geometrical characteristics. Both the steady and unsteady density-based RANS solver is used with the Realizable k-e model. Regarding the rotation of the wheel, three methods are utilised. Initially, simple rotating boundary conditions are applied, and then, the sliding mesh method is used. The application of the overset mesh method is also attempted, but on a slightly modified geometry that does not correspond exactly to the baseline case. All cases are compared to experimental results for several aspects of the flow and a Grid Convergence Study is performed for the steady state simulation in order to validate the results. Subsequently, more geometries are investigated. Grooves and realistic rims are added to the baseline geometry separately and combined in order to create three more cases. The alterations in the flow around them are studied by examining the forces coefficients, the vortical structures and the pressure field around the wheels. A comparison is also made regarding the computational cost for the rotation modelling methods and the forces distribution on different regions of the wheel. The appropriate height of the step used in the contact patch region is studied since it can affect the accuracy of every model significantly. Interesting results were produced, especially concerning the smallest step heights. The drag coefficient was affected greatly, but the lift was not influenced accordingly. Finally, three camber angles, 1, 2 and 3 degres are applied to the grooved tyre model. The flow field and specifically the wake is altered significantly, due to tilt of the vertical axis. However, there are no previous studies to compare the resulting structures that occur on the top of the wheel.