Simulation of coating flows with slip effects

Abstract

This work is concerned with the numerical prediction of wire coating flows. Both annular tube-tooling and pressure-tooling type extrusion–drag flows are investigated for viscous fluids. The effects of slip at die walls are analysed and free surfaces are computed. Flow conditions around the die exit are considered, contrasting imposition of no-slip and various instances of slip models for die wall conditions. Numerical solutions are computed by means of a time marching Taylor–Galerkin/pressure–correction finite element scheme, that demonstrates how slip conditions on die walls mitigate stress singularities at the die exit. For pressure-tooling and with appropriate handling of slip, reduction in shear rate at the die exit may be achieved. Maximum shear rates for tube-tooling are about one quarter of those encountered in pressure-tooling. Equivalently, extension rates peak at land entry, and tube-tooling values are one third of those observed for pressure-tooling. With slip and tube-tooling, peak shear values at die exit may be almost completely eliminated. Nevertheless, in contrast to the pressure-tooling scenario, this produces larger peak shear rates upstream within the land region than would otherwise be the case for no-slip. Copyright © 2000 John Wiley & Sons, Ltd.