On the Flow of a Polymer Melt Passing Over a Transverse Slot

Abstract

The phenomenon of hole pressure occurs whenever a polymeric or viscoelastic liquid flows over a depression in a conduit wall. Numerical simulations undertaken for the flow of an aqueous polyacrylamide melt passing over a transverse slot arc considered here. The fluid model used for this study is a White-Metzner constitutive equation describing the non-Newtonian behavior of the melt. The results were computed by an elastic-viscous split-stress finite clement method (EVSS-FEM). a mixed finite clement method incorporating the non-consistent streamline upwind scheme. For verification, the numerical algorithm was first applied to compute the corresponding flow of the upper-convected Maxwell fluid model, a special case of the Whitc-Metzner model characterized by constant viscosity and relation time. The resulting hole pressure (P_h) was evaluated for various Deborah numbers (De) and compared with the analytical prediction derived from the Higashitani-Pritchard (HP) theory. The agreement was found to be satisfactory for creeping flow in the low De range, for which the HP theory is valid. Subsequently, the hole pressure of this flow problem was predicted. The streamlines and pressure distribution along the channel walls arc also presented. Furthermore, the effects of fluid elasticity, shear thinning, the exponent in the viscosity function and the relaxation-time function, and slot geometry on the hole pressure were investigated.