Issue 42, 2023

Molecular dynamics simulation of the coalescence of surfactant-laden droplets

Abstract

We investigate the coalescence of surfactant-laden water droplets by using several different surfactant types and a wide range of concentrations by means of a coarse-grained model obtained by the statistical associating fluid theory. Our results demonstrate in detail a universal mass transport mechanism of surfactant across many concentrations and several surfactant types during the process. Coalescence initiation is seen to occur via a single pinch due to aggregation of surface surfactant, and its remnants tend to become engulfed in part inside the forming bridge. Across the board we confirm the existence of an initial thermal regime with constant bridge width followed by a later inertial regime with bridge width scaling roughly as the square root of time, but see no evidence of an intermediate viscous regime. Coalescence becomes slower as surfactant concentration grows, and we see evidence of the appearance of a further slowdown of a different nature for several times the critical concentration. We anticipate that our results provide further insights in the mechanisms of coalescence of surfactant-laden droplets.

Graphical abstract: Molecular dynamics simulation of the coalescence of surfactant-laden droplets

Supplementary files

Article information

Article type
Paper
Submitted
07 Aug 2023
Accepted
02 Oct 2023
First published
02 Oct 2023

Soft Matter, 2023,19, 8070-8080

Molecular dynamics simulation of the coalescence of surfactant-laden droplets

S. Arbabi, P. Deuar, M. Denys, R. Bennacer, Z. Che and P. E. Theodorakis, Soft Matter, 2023, 19, 8070 DOI: 10.1039/D3SM01046E

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