Flow of architectural coatings on complex surfaces; theory and experiment

A mathematical model is developed to predict the three-dimensional time-dependent flow of a nonNewtonian shear-thinning liquid coating on a non-planar substrate. The model employs the lubrication approximation and other simplifications. Results are compared with experimental observation of the drainage flow out of an axisymmetric indentation in a vertical substrate. A straightforward experimental method is developed to capture quantitative measurements of the evolving free-surface shapes. Two different architectural paints are used. The agreement between theory and experiment is good overall; however, agreement is better for one of the paints, presumably due to inadequate rheological modeling of the other. Improved understanding of the coating flow of these liquids can be expected to lead to improved products and processes.