Viscoelastic effects on drop deformation in a converging pipe flow

his paper reports finite-element simulations of drop deformation in converging flows in an xisymmetric conical geometry. The moving interface is captured using a diffuse-interface model nd accurate interfacial resolution is ensured by adaptive refinement of the grid. We have explored he effects of viscoelasticity on drop deformation when either the drop or the matrix is a Giesekus uid. Contrary to the popular belief that viscoelasticity in the drop hinders deformation and that in he matrix enhances deformation, we predict a more complex picture in which viscoelasticity in ither component may suppress or promote drop deformation depending on the capillary number a and the drop-to-matrix viscosity ratio . Smaller Ca and are conducive to the behavior entioned above, while large Ca and may produce the opposite effect. Both trends are explained y the reaction of the polymer stress to the inhomogeneous and transient deformation in the onverging flow field. Finally, this understanding reconciles contradictory results in the literature s opposite limits in the parameter space. © 2008 The Society of Rheology. DOI: 10.1122/1.2837525