Graduation Year

2021

Document Type

Thesis

Degree

M.S.C.E.

Degree Name

MS in Civil Engineering (M.S.C.E.)

Degree Granting Department

Civil and Environmental Engineering

Major Professor

Manjriker Gunaratne, Ph.D.

Co-Major Professor

Andres Tejada-Martinez, Ph.D.

Committee Member

Jeffrey Cunningham, Ph.D.

Keywords

ANSYS FLUENT, NASA, Numerical Modeling, Pneumatic Tire, Water Film Thickness

Abstract

Pneumatic hydroplaning has been identified as one of the major causes of wet weathertraffic accidents. Therefore, knowledge of potential hydroplaning speeds is crucial in designing roadways to reduce crash risks. It has been shown that the tire inflation pressure is the predominant factor affecting the hydroplaning speed while factors such as the water film thickness also contribute heavily to this phenomenon. Extensive research has been directed at the development of accurate models to predict the effects of vehicle characteristics, pavement conditions and water film thickness on hydroplaning. Current literature does not indicate any studies directed at understanding the effects of hydrodynamics on this phenomenon.

This research aims to study the hydrodynamic aspects of hydroplaning particularly with respect to the turbulent water flow conditions near the tire contact patch, using a computationally economical model. A numerical model has been formulated using ANSYS FLUENT for the simulation of a smooth tire sliding over a flooded pavement using the finite volume method. The current study adopts a generalized methodology that does not need a starting tire load and an inflation pressure, which essentially simplifies the complexity of the model. Alternative turbulence models in ANSYS FLUENT have been used in the simulation process and model performances have been compared to identify which conditions and solution methods would yield a better numerical accuracy. The model verification has been done with respect to the well-known National Aeronautics and Space Administration (NASA) equation which had been developed using the experimental findings involving trucks at Virginia’s NASA Langley research facility. The predictions of the developed model was also compared with those of the existing empirical and numerical models for a range of water film thicknesses. In addition, the model behavior under changing loads has also been investigated. From the theoretical analysis performed it was concluded that the accurate representation of hydrodynamics underneath the tire is crucial for numerically predicting the correct lift force on the tire. Furthermore, it was revealed that modeling of turbulence in flow is essential to obtain a better agreement with experimental results. Additionally, it was shown that changing the tire load has only a minor effect on the hydroplaning speed. Furthermore, streamlines of water flow and the pressure contours underneath and on sides of the tire obtained from the simulation illustrated the hydroplaning scenario reasonably clearly. Streamlines and pressure contours were verified by implementing a global conservation statement. Overall, it was found that a sufficiently accurate numerical model which is also computationally less expensive can be formulated by considering appropriate hydrodynamics of the water flow in the tire patch area.

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