A novel coarsening mechanism of droplets in immiscible fluid mixtures

In our daily lives, after shaking a salad dressing, we see the coarsening of oil droplets suspended in vinegar. Such a demixing process is observed everywhere in nature and also of technological importance. For a case of high droplet density, domain coarsening proceeds with interdroplet collisions a...

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Bibliographic Details
Published in:arXiv.org 2015-09
Main Authors: Shimizu, Ryotaro, Tanaka, Hajime
Format: Article
Language:English
Subjects:
Accidental collisions
Coagulation
Coalescing
Coarsening
Composition
Demixing
Droplets
Miscibility
Shaking
Surface tension
Vinegar
Online Access:Get full text
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Summary:In our daily lives, after shaking a salad dressing, we see the coarsening of oil droplets suspended in vinegar. Such a demixing process is observed everywhere in nature and also of technological importance. For a case of high droplet density, domain coarsening proceeds with interdroplet collisions and the resulting coalescence. This phenomenon has been explained primarily by the so-called Brownian coagulation mechanism: stochastic thermal forces exerted by molecules induce random motion of individual droplets, causing accidental collisions and subsequent interface-tension driven coalescence. Contrary to this, we demonstrate that the droplet motion is not random, but hydrodynamically driven by the composition Marangoni force due to an interfacial tension gradient produced in each droplet as a consequence of composition correlation among droplets. This alters our physical understanding of droplet coarsening in immiscible liquid mixtures on a fundamental level.
ISSN:2331-8422
DOI:10.48550/arxiv.1509.03385