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Finite element approximation of a two-layered liquid filmin the presence of insoluble surfactants

Published online by Cambridge University Press:  30 July 2008

John W. Barrett
Affiliation:
Department of Mathematics, Imperial College, London, SW7 2AZ, UK. [email protected]
Linda El Alaoui
Affiliation:
Department of Mathematics, Imperial College, London, SW7 2AZ, UK. [email protected]
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Abstract

We consider a system of degenerate parabolic equations modelling a thin film, consisting of two layers of immiscible Newtonian liquids, ona solid horizontal substrate. In addition, the model includes the presence of insoluble surfactants onboth the free liquid-liquid and liquid-air interfaces,and the presence of both attractive and repulsive van der Waals forcesin terms of the heights of the two layers. We show that this system formally satisfies a Lyapunov structure,and a second energy inequality controlling the Laplacianof the liquid heights.We introduce a fully practical finite element approximation of this nonlinear degenerate parabolic system, that satisfies discrete analoguesof these energy inequalities. Finally, we prove convergence of this approximation,and hence existence of a solutionto this nonlinear degenerate parabolic system.

Type
Research Article
Copyright
© EDP Sciences, SMAI, 2008

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