Nonlinear chemoconvection in the methylene-blue–glucose system: two-dimensional shallow layers

Pons, A.J., Batiste, O. and Bees, M.A. (2008) Nonlinear chemoconvection in the methylene-blue–glucose system: two-dimensional shallow layers. Physical Review E, 78(1), 016316. (doi: 10.1103/PhysRevE.78.016316)

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Interfacial hydrodynamic instabilities arise in a range of chemical systems. One mechanism for instability is the occurrence of unstable density gradients due to the accumulation of reaction products. In this paper we conduct two-dimensional nonlinear numerical simulations for a member of this class of system: the methylene-blue–glucose reaction. The result of these reactions is the oxidation of glucose to a relatively, but marginally, dense product, gluconic acid, that accumulates at oxygen permeable interfaces, such as the surface open to the atmosphere. The reaction is catalyzed by methylene-blue. We show that simulations help to disassemble the mechanisms responsible for the onset of instability and evolution of patterns, and we demonstrate that some of the results are remarkably consistent with experiments. We probe the impact of the upper oxygen boundary condition, for fixed flux, fixed concentration, or mixed boundary conditions, and find significant qualitative differences in solution behavior; structures either attract or repel one another depending on the boundary condition imposed. We suggest that measurement of the form of the boundary condition is possible via observation of oxygen penetration, and improved product yields may be obtained via proper control of boundary conditions in an engineering setting. We also investigate the dependence on parameters such as the Rayleigh number and depth. Finally, we find that pseudo-steady linear and weakly nonlinear techniques described elsewhere are useful tools for predicting the behavior of instabilities beyond their formal range of validity, as good agreement is obtained with the simulations.

Item Type:Articles
Glasgow Author(s) Enlighten ID:Bees, Dr Martin
Authors: Pons, A.J., Batiste, O., and Bees, M.A.
Subjects:Q Science > QD Chemistry
College/School:College of Science and Engineering > School of Mathematics and Statistics > Mathematics
Journal Name:Physical Review E
Journal Abbr.:Phys. Rev. E
Publisher:American Physical Society
ISSN (Online):1550-2376
Copyright Holders:Copyright © 2008 American Physical Society
First Published:First published in Physical Review E 78(1):016316
Publisher Policy:Reproduced in accordance with the copyright policy of the publisher

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