A comparison of boundary element and finite element methods for modeling axisymmetric polymeric drop deformation

A modified boundary element method (BEM) and the DEVSS-G finite element met hod (FEM) are applied to model the deformation of a polymeric drop suspende d in another fluid subjected to start-up uniaxial extensional flow. The eff ects of viscoelasticity, via the Oldroyd-B differential model, are consider ed for the drop phase using both FEM and BEM and for both the drop and matr ix phases using FEM. Where possible, results are compared with the linear d eformation theory. Consistent predictions are obtained among the BEM. FEM, and linear theory for purely Newtonian systems arid between FEM and linear theory for fully viscoelastic systems. FEM and BEM predictions for viscoela stic drops in a Newtonian matrix agree very well at short times but differ at longer times, with worst agreement occurring as critical flow strength i s approached. This suggests that the dominant computational advantages held by the BEM over the FEM for this and similar problems may diminish or even disappear when the issue of accuracy is appropriately considered. Fully vi scoelastic problems, which are only feasible using the FEM formulation, she d new insight on the role of viscoelasticity of the matrix fluid in drop de formation. Copyright (C) 2001 John Wiley & Sons, Ltd.