COATING FLOWS

Abstract

▪ Abstract Coating is the process of applying thin liquid layers to a substrate, often a moving web. Complex coating processes can be approached through examination of their fluid mechanical components. The flow elements reviewed in this article include the boundary layer along a moving wall, the dynamic wetting line, withdrawal from a pool, flow metered by a narrow channel, die flow, flow on an incline, the freely falling liquid curtain, premetered coating with a small gap, and flow after coating. Although some flow elements are well studied and understood, others require additional investigation. Genuinely predictive modeling of complex coating processes is not yet possible and coating practice remains largely empirical. Nonetheless, coating science is sufficiently advanced that physical insights and mathematical models greatly benefit design and practice.