Numerical studies of fiber suspensions in an axisymmetric radial diverging flow: the effects of modeling and numerical assumptions

Abstract

Until recently, most simulations of fiber suspensions have been developed using the Hele-Shaw approximation. Therefore, the fluid behavior around the melt-front, solid walls, weldlines, gates, ribs, and sudden thickness changes could not be predicted accurately. In this study, a finite element method (FEM) analysis of an axisymmetric three-dimensional geometry was performed using the pseudo-concentration method (PCM) as a melt-front capturing technique for fiber suspensions. The non-Newtonian governing equations were solved using a streamline upwind Petrov-Galerkin (SUPG) FEM to maintain the stability of the convection-dominated problem. Second-order orientation tensors with a closure model were adopted to predict the evolution of fiber suspensions. A center-gated disk geometry was used as a benchmark test problem because of the complicated nature of its flow history. The predictions were compared with experimental data, and the coupling effects between the fluid and fibers, the effects of fountain-flow, initial conditions (sprue effect), closure approximation, and processing conditions were observed. Fountain-flow effect on the fiber orientation state has been found to be most significant of these effects. (C) 2002 Elsevier Science B.V. All rights reserved.