Optimizing coating processes can be difficult due to the small scale of fluid motion and the influence of effects such as wall adhesion and surface tension. FLOW-3D provides a convenient way to analyze these processes without having to resort to costly laboratory experiments. FLOW-3D's models simulate surface tension gradients due to temperature variations, heat transfer, vaporization, condensation, solute transport and density-driven flows.
This is a single-layer slot coating apparatus, with a coating width of 2cm, and a thickness between the die face and web 250µm. The slot gap is 1.02mm, and both upstream and downstream die surfaces are 1.5mm long. In this example, the web speed is 13.3cm/s, and the fluid applied is a Carreau fluid with zero-shear viscosity 700 cpoise, η∞=40cpoise, density 1200kg/m3 and surface tension 61 mN/m. The flow rate is 1.178g/s, with a resulting average coating thickness 73.8µm. The static contact angle between the coating fluid and all surfaces is 30°. The animation shows the first 0.4s after initiation of fluid flow, and shows the attachment to the web and subsequent development of the coating bead. The bead is stabilized by an upstream vacuum of 2kPa. Go to the Slot Coating page for more information about modeling this process.
Simulating Viscoelastic Coating Flows
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