Numerical simulation of tube-tooling cable-coating with polymer melts

This study investigates the numerical solution of viscous and viscoelastic flows for tube-tooling die-extrusion coating using a hybrid nite element/nite volume discretisation (fe/fv). Such a complex polymer melt extrusion-draw-coating flow displays a dynamic contact line, slip, die-swell and two separate free-surfaces, presenting an inner and outer conduit surface to the melt-coating. The practical interest lies in determining efficient windows for process control over variation in material properties, stressing levels generated and vacuum pressure levels imposed. The impact of shear-thinning is also considered. Extensive reference is made throughout to viscous inelastic counterpart solutions. Attention is paid to the influence and variation in relevant parameters of Weissenberg number (We), solvent-fraction (beta) and second normal difference (N (2)) (xi parameter for EPTT). The impact of model choice and parameters upon field response is described in situ through, pressure-drops, rates of deformation and stress. Various numerical alternative strategies, their stability and convergence issues are also addressed. The numerical scheme solves the momentum-continuity-surface equations by a semi-implicit time-stepping Taylor-Galerkin/pressure-correction (TGPC) finite element (parent-cell) method, whilst invoking a sub-cell cell-vertex fluctuation distribution finite volume scheme for the constitutive stress equation. The hyperbolic aspects of the constitutive equation are addressed discretely through upwind Fluctuation Distribution techniques, whilst temporal and source terms are consistently accommodated through medium-dual-cell schemes. The dynamic solution of the moving boundary problem may be resolved by either separating the solution process for each free-surface section (decoupling), or coupling both sections and solving simultaneously. Each involves a surface height location method, with dependency on surface nodal velocities and surface element sections; two such schemes are investigated. Dedicated and localised shock-capturing techniques are introduced to handle solution singularities as disclosed by die-swell, slip and moving contact lines.