Computer simulation of the laminar nozzle flow of a non-Newtonian fluid in a rubber extrusion process by the finite volume method and experimental comparison

Résumé

The aim of this work is to describe the computer simulation of the laminar flow through a nozzle in a rubber extrusion process by the finite volume method (FVM). The liquid rubber is a highly compliant material, whose behavior is not described by the Newtonian constitutive relations, and whose underlying physics is not yet completely understood. The processing and transport of such fluids are central problems in the polymer, plastics and automotive industries. Non-Newtonian behavior manifests itself in a number of different ways. This fluid exhibits a shear rate dependent viscosity, with 'shear thinning', that is, decreasing viscosity with increasing shear rate, being the most prevalent behavior. We have taken the power-law model in order to simulate this rubber extrusion process, which has the form μ = KI2(n - 1) / 2, where μ, I2, n and K are termed the dynamic viscosity, the second invariant of the rate of deformation tensor, the power-law index and the consistency, respectively. These last two parameters were obtained from experimental tests and used in a computer simulation. In this work we have modeled two types of rubbers and different inlet pressures, for a type of nozzle, in order to calculate the outlet velocity distribution of the rubber jet in this extrusion process. Finally we have compared the numerical and experimental results, so that this model is consistent with the experimental evidence. © 2007 Elsevier B.V. All rights reserved.