Coalescence of Low-Viscosity Fluids in Air

TL;DR

This study uses electrical measurements to investigate the initial stages of coalescence between low-viscosity drops, revealing a new asymptotic regime and supporting a model of slightly deformed interfaces during coalescence.

Contribution

It introduces an electrical method to analyze early coalescence, discovering a new asymptotic behavior not predicted by previous theories.

Findings

Identification of a new asymptotic regime during early coalescence

Electrical measurements provide insights into bridge radius and height dynamics

Results support a model of coalescence with slightly deformed interfaces

Abstract

An electrical method is used to study the early stages of coalescence of two low-viscosity drops. A drop of aqueous NaCl solution is suspended in air above a second drop of the same solution which is grown until the drops touch. At that point a rapidly widening bridge forms between them. By measuring the resistance and capacitance of the system during this coalescence event, one can obtain information about the time dependence of the characteristic bridge radius and its characteristic height. At early times, a new asymptotic regime is observed that is inconsistent with previous theoretical predictions. The measurements at several drop radii and approach velocities are consistent with a model in which the two liquids coalesce with a slightly deformed interface.