Drop dynamics on the beads-on-string structure for viscoelastic jets: A numerical study

Abstract

It is well known that a viscoelastic jet breaks up much more slowly than a Newtonian jet. Typically, it evolves into the so-called beads-on-string structure, where large drops are connected by thin threads. The slow breakup process provides the viscoelastic jet sufficient time to exhibit some new phenomena. The aim of this paper is to investigate the drop dynamics of the beads-on-string structure. This includes drop migration, drop oscillation, drop merging and drop draining. We will use a 1D Oldroyd-B model for the viscoelastic jet, and solve this model numerically by an explicit finite difference method. Close to exponential draining of the filament, we found that the variation of the axial elastic force in the filament is roughly four times larger than the variation of the capillary force with opposite sign. This fact implies that the elastic force is responsible for the drop migration and oscillation. Our study of the drop draining process shows that the elastic force also plays an important role here, allowing the liquid to flow from smaller drops into larger drops through the filament.