Sub-Newtonian coalescence in polymeric fluids

TL;DR

This paper introduces a theoretical framework for understanding sub-Newtonian coalescence in polymeric fluids, revealing a new arrested coalescence regime and validating predictions with experiments on PEO.

Contribution

It unifies constitutive laws under high Weissenberg flow to describe coalescence, proposing a new regime and a novel time scale incorporating molecular parameters.

Findings

Identification of a sub-Newtonian coalescence regime.

Prediction of arrest angle proportional to Ec^{-1/2}.

Validation with high-speed imaging experiments.

Abstract

We present a theoretical framework for capturing the coalescence of a pendant drop with a sessile drop in polymeric fluids. The framework is based on the unification of various constitutive laws under high Weissenberg creeping flow limit. Our results suggests that the phenomenon comes under a new regime namely, the sub-Newtonian regime followed by the limiting case of arrested coalescence with the arrest angle $\theta_{arrest}\propto Ec^{-1/2}$, where $Ec$ is the Elasto-capillary number. Further, we propose a new time scale $T^*$ integrating the continuum variable $Ec$ and the macromolecular parameter $N_e$, the entanglement density to describe the liquid neck evolution. Finally, we validate the framework with high speed imaging experiments performed across different molecular weights of Poly(ethylene oxide) (PEO).