Electronic Thesis and Dissertation Repository

Degree

Master of Engineering Science

Program

Mechanical and Materials Engineering

Supervisor

Roger.E. Khayat

2nd Supervisor

Andrew Hrymak

Joint Supervisor

Abstract

A thin layer of film is developed on the surface of a substrate in the dip coating process where the substrate is initially immersed into the coating fluid and then withdrawn continuously from the coating fluid bath. In this study a two dimensional flow of the thin film for a Newtonian fluid is examined theoretically by dividing the film into three separate regions. A general formulation is developed for a thin film flow, which then simplifies for each region upon considering appropriate assumptions to each region. The influence of inertia and surface tension in the presence of gravity is investigated for the steady flow only. The thin film equations are solved by expanding the flow field in terms of orthonormal shape functions in the transverse direction. A spectral approach is adopted instead of previously used depth-averaging technique to predict the final coating thickness as a function of the withdrawal speed and the fluid properties. The spectral solution provides a very good agreement with the experimental results. It is found that the flow field is highly dependent on inertia. The effect of inertia is investigated on the free surface profile, length of the domain, thickness of the film and the fluid flow rate. A numerical model using the Volume of fluid (VOF) method is also developed in the current study which is validated by the spectral solution and the experimental results.

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