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Two-dimensional effects in double-diffusive convection

Published online by Cambridge University Press:  29 March 2006

J. S. Turner  and
C. F. Chen
J. S. Turner
Affiliation:
Department of Applied Mathematics and Theoretical Physics, University of Cambridge
C. F. Chen
Affiliation:
Mechanical, Industrial and Aerospace Engineering Department, Rutgers University, New Brunswick, New Jersey 08903
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Abstract

The limitations of existing one-dimensional experiments on double-diffusive convection are discussed, and a variety of new two-dimensional phenomena are described. We have used the sugar-salt system and shadowgraph photography to make exploratory studies of motions which can arise in a fluid with two smooth, opposing, vertical concentration gradients, with and without horizontal gradients. Many different effects have been observed, the most important of which are the following, (a) In the ‘finger’ case, local disturbances can propagate rapidly as wave motions, which cause a simultaneous breakdown to convection over large horizontal distances. (b) Layers formed in the’ diffusive’ sense overturn locally to produce fingers, but propagate more slowly, as convective rather than wave motions, (c) A series of layers, separated by diffusive interfaces, can become unstable, in the sense that successive layers merge in time as their densities become equal, (d) The presence of horizontally separated sources of water of similar density but different T, S characteristics can lead to the development of strong vertical gradients and extensive quasi-horizontal layering.

Most of our results are qualitative, but it is hoped that they will stimulate further quantitive work on each of the new processes described. It is already clear that much more needs to be done before the mechanism of formation of layers observed in the ocean can be regarded as properly understood.

Type
Research Article
Information
Journal of Fluid Mechanics , Volume 63 , Issue 3 , 29 April 1974 , pp. 577 - 592
Copyright
© 1974 Cambridge University Press

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