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Experimental studies of the deformation and breakup of a synthetic capsule in steady and unsteady simple shear flow

Published online by Cambridge University Press:  26 April 2006

K. S. Chang  and
W. L. Olbricht
K. S. Chang
Affiliation:
School of Chemical Engineering, Cornell University, Ithaca, NY 14853, USA Present address: Kimberly-Clark, 2100 Winchester Road, Neenah, WI 54957-0999, USA.
W. L. Olbricht
Affiliation:
School of Chemical Engineering, Cornell University, Ithaca, NY 14853, USA
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Abstract

An experimental study is reported of the motion, deformation, and breakup of a synthetic capsule that is freely suspended in Couette flow. The capsule is a liquid drop surrounded by a thin polymeric membrane. The shape and orientation of the capsule are measured in steady flow and following the start-up of Couette flow. Results are compared with predictions of the small-deformation theory of Barthes-Biesel and co-workers. The data suggest that the capsule membrane is viscoelastic, and comparisons with theory yield values of the membrane elastic modulus and the membrane viscosity. The values of the elastic modulus of the capsule membrane deduced from the flow data are compared with independent measurements for the same capsule.

When the flow-induced deformation becomes sufficiently large, the capsules break. Breakup begins at points on the membrane surface near the principal strain axis of the undisturbed flow. By examining the local deformation within the membrane, it is shown that breakup is correlated with local thinning of the membrane and is initiated at points where the thickness is a minimum.

Type
Research Article
Information
Journal of Fluid Mechanics , Volume 250 , May 1993 , pp. 609 - 633
Copyright
© 1993 Cambridge University Press

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