Simulation of Coating Flows with Slip Effects
Summary : 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 demonstrate how slip conditions on die walls mitigate stress singularities at 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.