Abstract
Abstract
Highlights
The coating of non-planar discrete objects is a common manufacturing step for a wide variety of products (Castro et al 2002; Heller et al 2003; Fujitaka & Kobayashi 2006; Benjamin et al 2008; Chen & Ho 2009; Lee et al 2016; Cade & Xinwe 2017; Chappa, Bach & Macgregor 2017; Keefer & Bosch 2018)
We examine the effects of topography on coating behaviour in the presence of gravity, where the coating may sag under its own weight
For axially patterned cylinders, the free surface on the upward-moving side of the cylinder is shown at different times below the critical rotation rate in figure 15(a,b) and above the critical rotation rate in figure 15(c,d)
Summary
The coating of non-planar discrete objects is a common manufacturing step for a wide variety of products (Castro et al 2002; Heller et al 2003; Fujitaka & Kobayashi 2006; Benjamin et al 2008; Chen & Ho 2009; Lee et al 2016; Cade & Xinwe 2017; Chappa, Bach & Macgregor 2017; Keefer & Bosch 2018). Studying the evolution of coatings on non-planar objects is difficult due to the complicated shapes of some objects and the large number of competing forces that govern coating flows. Topography on the object’s surface may alter the competition between viscous, surface-tension, centrifugal and gravitational forces that control coating thickness and uniformity. A commonly studied model problem involves the flow of a thin liquid film on a smooth, circular cylinder that rotates about its horizontal axis. By considering the balance between viscous and gravitational forces in the absence of surface tension, Moffatt derived a critical rotation rate above which a steady, smooth, and asymmetric coating is supported by cylinder rotation (Moffatt 1977): 2π 2 H2 ρgR
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