Influence of insoluble surfactant on the deformation and breakup of a bubble or thread in a viscous fluid

HAMEED, M. and SIEGEL, M. and YOUNG, Y.-N. and LI, J. and BOOTY, M. R. and PAPAGEORGIOU, D. T. (2008) Influence of insoluble surfactant on the deformation and breakup of a bubble or thread in a viscous fluid. Journal of Fluid Mechanics, 594. pp. 307-340. ISSN 0022-1120 DOI 10.1017/S0022112007009032

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Official URL: http://dx.doi.org/10.1017/S0022112007009032

Abstract

The influence of surfactant on the breakup of a prestretched bubble in a quiescent viscous surrounding is studied by a combination of direct numerical simulation and the solution of a long-wave asymptotic model. The direct numerical simulations describe the evolution toward breakup of an inviscid bubble, while the effects of small but non-zero interior viscosity are readily included in the long-wave model for a fluid thread in the Stokes flow limit. The direct numerical simulations use a specific but realizable and representative initial bubble shape to compare the evolution toward breakup of a clean or surfactant-free bubble and a bubble that is coated with insoluble surfactant. A distinguishing feature of the evolution in the presence of surfactant is the interruption of bubble breakup by formation of a slender quasi-steady thread of the interior fluid. This forms because the decrease in surface area causes a decrease in the surface tension and capillary pressure, until at a small but non-zero radius, equilibrium occurs between the capillary pressure and interior fluid pressure. The long-wave asymptotic model, for a thread with periodic boundary conditions, explains the principal mechanism of the slender thread's formation and confirms, for example, the relatively minor role played by the Marangoni stress. The large-time evolution of the slender thread and the precise location of its breakup are, however, influenced by effects such as the Marangoni stress and surface diffusion of surfactant.

Item Type: Article
Uncontrolled Keywords: BPI
Subjects: 99 - Other
Divisions: 99 - Other
Journal or Publication Title: Journal of Fluid Mechanics
Volume: 594
Page Range: pp. 307-340
Identification Number: 10.1017/S0022112007009032
Depositing User: Sarah Humbert
Date Deposited: 21 Jul 2010 20:29
Last Modified: 23 Jul 2013 09:57
URI: http://eprints.esc.cam.ac.uk/id/eprint/1493

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