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Thinning and disturbance growth in liquid films mobilized by continuous surfactant delivery

Fischer, Benjamin J. and Troian, Sandra M. (2003) Thinning and disturbance growth in liquid films mobilized by continuous surfactant delivery. Physics of Fluids, 15 (12). pp. 3837-3845. ISSN 1070-6631. doi:10.1063/1.1623489.

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A generalized linear stability analysis is applied to the case of a thin liquid film propelled to spread by a continuous supply of surfactant. The time-dependent base states for the film thickness and surfactant concentration give rise to a nonautonomous system describing disturbance propagation. As a first approximation, the nonautonomous operator is treated as time independent, thereby reducing the system of equations to a standard eigenvalue problem. For the range of parameters investigated, this modal approximation reveals a band of unstable modes corresponding to the growth of transverse, sinusoidal corrugations. A transient growth analysis of the fully time-dependent system, which requires the solution of an initial value problem, also signals the possibility of large disturbance growth. In both cases, significant amplification of infinitesimal disturbances can be traced to the region of the film most rapidly thinned by Marangoni stresses, which is characterized by large interfacial curvature and a sharp variation in shear stress. In contrast to previous models implementing a finite surfactant source that predict asymptotic stability, large transient growth and asymptotic instability are possible for the case of sustained surfactant release.

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Troian, Sandra M.0000-0003-1224-6377
Additional Information:©2003 American Institute of Physics. (Received 11 February 2003; accepted 10 September 2003; published online 5 November 2003) Financial support from the National Science Foundation (CTS-0088774 and DMR-0213706), Unilever Research U.S., and the U.S. Army (ARDEC) is gratefully acknowledged.
Subject Keywords:liquid films; surfactants; eigenvalues and eigenfunctions; initial value problems
Issue or Number:12
Record Number:CaltechAUTHORS:FISpof03
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Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:4958
Deposited By: Archive Administrator
Deposited On:15 Sep 2006
Last Modified:08 Nov 2021 20:21

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