Effect of Elasticity Parameter on Viscoelastic Fluid in Pipe Flow Using Extended Pom-Pom Model

Abstract

In this study prediction of the steady-state flow of branched polymer melts in pipe geometry with finite volume method is presented. Our analysis in this study revealed that; for normal-stress τθθ , the XPP model can predict this tensor unlike the other viscoelastic models such as PTT or Gieskus which can not predict τθθ for viscoelastic fluid in two dimensional pipe flows. The fluid is modelled using a modification of the Pom-Pom model known as the single eXtended Pom-Pom (XPP) where viscoelastic fluid is typically a commercial low-density polyethylene. In finite volume method, the operator-integration is used to discretize the governing equations in space or control volume. An iterative solution algorithm that decouples the computation of momentum from that of stress is used to solve the discrete equations. Numerical results are presented, including the profiles of all relevant stresses, the axial velocity, stretch and the viscosity across the gap, demonstrating the performance of the model predictions. The influence of elasticity parameter on flow behaviour is studied, which demonstrates in particular, the dependence of velocity and stresses distribution as a function of Weissenberg number is analyzed. Also, the effect of Weissenberg number on pressure gradient has been considered. Finally, verification of the present model was made by comparing to the Generalized Newtonian Fluid (GNF) model.