Layered Droplet Microstructures in Sheared Emulsions: Finite-Size Effects

Published

November 1, 2002

Author(s)

Jai A. Pathak, M C. Davis, Steven D. Hudson, Kalman D. Migler

Abstract

We investigate the influence of confinement on the steady state microstructure of emulsions sheared between parallel plates, in a regime where the average droplet dimension is comparable to the gap width between the confining walls. Utilizing droplet velocimetry, we find that the droplets can organize into discrete layers under the influence of shear. The number of layers decreases from two (at relatively higher shear rates) to one (at lower shear rates), as the drops grow larger due to coalescence. We argue that the layering and overall composition profile may be controlled by the interplay of droplet collisions (which can cause separation of droplet centers in the velocity gradient direction), droplet migration towards the centerline and droplet packing constraints. We have also studied the effects of mixture composition on droplet microstructure, and summarized these results in the form of a morphology diagram in the parameter space of mass fraction and shear rate. We find that formation of strings of the suspended phase (reported earlier by our group in flow-visualization studies on confined emulsions) is observed over a broad composition window. We also find that there is a stable (nontransient) morphology wherein the droplets are arranged in highly ordered pearl-necklace chain structures.

Citation

Journal of Colloid and Interface Science

Volume

256

Issue

No. 2

Pub Type

Journals

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Keywords

collisions, confinement, emulsion, finite size effects, layering, wall migration

Citation

Pathak, J. , Davis, M. , Hudson, S. and Migler, K. (2002), Layered Droplet Microstructures in Sheared Emulsions: Finite-Size Effects, Journal of Colloid and Interface Science, [online], https://tsapps.nist.gov/publication/get_pdf.cfm?pub_id=851987 (Accessed March 5, 2025)