Numerical simulation of the dip-coating process with wall effects on the coating film thickness

Abstract

The dip-coating process for liquid film deposition on cylindrical substrates is numerically simulated, and the effects of the coating bath walls proximity to the substrate are investigated for the deposited film thickness. In the present work, the hydrodynamics of non-Newtonian liquid films are studied, applying Carreau and power law models. The free surface position is determined by the volume of fluid technique in a three-dimensional system, while the impacts of density, viscosity, and surface tension are taken into account. The momentum and mass balance, alongside the constitutive equations, were solved for dip-coating process using numerical simulations in an open source CFD software package of OpenFOAM. Numerical outcomes are validated with experimental data over a large range of withdrawal velocities up to 6 m/s. Also good agreement is obtained for numerical simulation results with experimental data for coating thickness, considering the proximity effects of bath walls to the cylindrical substrate being withdrawn from a coating bath.