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 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 noslip.

Numerical simulation of bubble growth in Newtonian and viscoelastic filaments undergoing stretching

“…The implementation of such a boundary condition has customarily been followed in the literature as a means for avoiding singularities [28,29]. Newby and Chaudhury have experimentally confirmed that viscoelastic adhesives have larger slip zones than Newtonian liquids on segmentally mobile organic surfaces at and near crack tip regions [30].…”

“…In spherical coordinates, Eq. (13) boils down to r = −β(r)u r , where β(r) is the slip coefficient defined through β = 1/L slip with L slip denoting the (dimensionless) slip length (i.e., the size of the region near the contact line that slips); the no-slip case is recovered when L slip → 0 [28,29]. The consequences of such a slip boundary condition on bubble growth will be compared to those derived with the no slip boundary condition in Section 4.…”

Computation of weakly‐compressible highly‐viscous liquid flows

“…This has accommodated model to complex flows exemplified through free-surface flows (Ngamaramvaranggul and Webster, 2000a), wire-coating (Ngamaramvaranggul and Webster, 2000b) and dough mixing applications (Baloch et al, 2002). Our present goal is to elaborate the constructive steps to incorporate weak-compressibility upon such a formulation, where we have polymeric liquid flow applications firmly in mind (viscous form, viscoelastic to follow).…”

Numerical simulation of viscoelastic flows using integral constitutive equations: A finite difference approach

“…Therefore, it comes as no surprise that the majority of numerical investigations relies on differential constitutive equations, using diverse numerical methods such as finite elements (e.g. [23,27,28,7], to cite only a few), finite volumes (e.g. [26,52]) and finite difference (e.g.…”