Journal
JOURNAL OF NON-NEWTONIAN FLUID MECHANICS
Volume 144, Issue 2-3, Pages 87-97Publisher
ELSEVIER SCIENCE BV
DOI: 10.1016/j.jnnfm.2007.04.002
Keywords
extensional viscosity; contraction flow; rheology; Boger fluids
Categories
Ask authors/readers for more resources
An approximate analytical solution is presented to predict the flow, vortex and pressure drop behaviour in abrupt axisymmetric contractions. This solution is developed to identify the effect of fluids which exhibit large Trouton ratios at large extensional rates despite having a constant shear viscosity. This behaviour approximates that shown in dilute polymeric solutions, although any transient effects are neglected by removing any strain dependence of the extensional viscosity and by assuming that the steady-state extensional viscosity undergoes a step change from a Trouton ratio of 3 to a large Trouton ratio at a critical rate. The predictions compare well to available experimental results for dilute to semi-dilute solutions of a flexible polymer, polystyrene, prior to the onset of elastic instabilities and for dilute solutions of a semi-rigid polymer, xanthan. The results show that vortex behaviour is determined by the fluid's characteristic time (through the magnitude of the Weissenberg number of the flow), while the steady-state extensional viscosity is of far more importance than transient effects in determining the steady-state pressure drop. Crown Copyright (c) 2007 Published by Elsevier B.V All rights reserved.
Authors
I am an author on this paper
Click your name to claim this paper and add it to your profile.
Reviews
Recommended
No Data Available