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Role of surfactant-induced Marangoni stresses in drop-interface coalescence

Published online by Cambridge University Press:  23 August 2021

C.R. Constante-Amores
Department of Chemical Engineering, Imperial College London, South Kensington Campus, London SW7 2AZ, UK
A. Batchvarov
Department of Chemical Engineering, Imperial College London, South Kensington Campus, London SW7 2AZ, UK
L. Kahouadji
Department of Chemical Engineering, Imperial College London, South Kensington Campus, London SW7 2AZ, UK
S. Shin
Department of Mechanical and System Design Engineering, Hongik University, Seoul 04066, Republic of Korea
J. Chergui
Centre National de la Recherche Scientifique (CNRS), Laboratoire Interdisciplinaire des Sciences du Numérique (LISN), Université Paris Saclay, 91400 Orsay, France
D. Juric
Centre National de la Recherche Scientifique (CNRS), Laboratoire Interdisciplinaire des Sciences du Numérique (LISN), Université Paris Saclay, 91400 Orsay, France
O.K. Matar*
Department of Chemical Engineering, Imperial College London, South Kensington Campus, London SW7 2AZ, UK
Email address for correspondence:


We study the effect of surfactants on the dynamics of a drop-interface coalescence using full three-dimensional direct numerical simulations. We employ a hybrid interface-tracking/level-set method, which takes into account Marangoni stresses that arise from surface-tension gradients, interfacial and bulk diffusion and sorption kinetic effects. We validate our predictions against the experimental data of Blanchette and Bigioni (Nat. Phys., vol. 2, issue 4, 2006, pp. 254–257) and perform a parametric study that demonstrates the delicate interplay between the flow fields and those associated with the surfactant bulk and interfacial concentrations. The results of this work unravel the crucial role of the Marangoni stresses in the flow physics of coalescence, with particular attention paid to their influence on the neck reopening dynamics in terms of stagnation-point inhibition, and near-neck vorticity generation. We demonstrate that surfactant-laden cases feature a rigidifying effect on the interface compared with the surfactant-free case, a mechanism that underpins the observed surfactant-induced phenomena.

JFM Papers
© The Author(s), 2021. Published by Cambridge University Press

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