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Droplet Microstructure and String Stability in Sheared Emulsions: Role of Finite-Size Effects

Published

Author(s)

Jai A. Pathak, E Robertson, Steven D. Hudson, Kalman D. Migler

Abstract

We discuss the influence of confinement on the microstructure of emulsions in steady shear flow fields and present initial results on experiments on stability of confined strings. We use flow visualization to get information about the structure and velocity of droplets and strings. In experiments on model emulsions comprising polyisobutylene and poly(dimethylsiloxane), using a well-defined step-down protocol in shear, we find the organization of droplets in layers, starting with two layers at high shear rates and then one layer at lower shear rates. We reiterate arguments on the physics behind separation of droplets in layers. Strings formed under confinement can remain stable upon an increase in shear rate, so long as confinement effects due to the walls are still felt. Upon reduction in shear, strings survive until interfacial stress effects overwhelm shear stress, when droplets are recovered. Direct observation helps in unambiguous identification of string breakup and relaxation mechanisms.
Proceedings Title
American Chemical Society Meeting | 224th | Nonlinear Dynamics in Polymeric Systems | American Chemical Society
Volume
869
Conference Dates
August 18-22, 2002
Conference Title
ACS Symposium Series

Keywords

collisions, droplets, emulsions, end-pinching, finite-size effects, layering, Rayleigh-Taylor Instability, strings, wall migration

Citation

Pathak, J. , Robertson, E. , Hudson, S. and Migler, K. (2004), Droplet Microstructure and String Stability in Sheared Emulsions: Role of Finite-Size Effects, American Chemical Society Meeting | 224th | Nonlinear Dynamics in Polymeric Systems | American Chemical Society, [online], https://tsapps.nist.gov/publication/get_pdf.cfm?pub_id=852127 (Accessed June 23, 2024)

Issues

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Created February 1, 2004, Updated February 19, 2017