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Observed flow patterns at the initiation of convection in a horizontal liquid layer heated from below

Published online by Cambridge University Press:  29 March 2006

E. F. C. Somerscales  and
T. S. Dougherty
E. F. C. Somerscales
Affiliation:
Rensselaer Polytechnic Institute, Troy, New York 12181
T. S. Dougherty
Affiliation:
Rensselaer Polytechnic Institute, Troy, New York 12181 Present address: Western Electric Engineering Research Center, Princeton, New Jersey 08540.
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Abstract

An experimental investigation has been made of the flow patterns at the initiation of convection in a layer of a high Prandtl number liquid confined between rigid, horizontal surfaces and heated from below. The experiment was designed to overcome the limitations of earlier experiments and to correspond closely to the conditions of the theory. In particular, the upper and lower rigid surfaces which enclosed the layer were made of copper which has a high thermal conductivity. To aid in the analysis of the experimental results some supplementary observations of the flow patterns were made using a glass upper plate. For small fluid depths and large temperature differences between the upper and lower surface the initial flow was in the form of hexagonal cells as predicted theoretically. With increasing Rayleigh number the cellular flow appeared to transform into rolls as predicted. For large fluid depths and small temperature differences only circular plan-form rolls were observed. This is in agreement with the results of other experimenters. It is tentatively proposed that this non-appearance of an initial cellular flow is due to the shape of the test chamber having a dominating influence on the flow pattern when the temperature gradient in the fluid is small. Measurements were also made of the development time for the flow patterns and the critical Rayleigh number.

Type
Research Article
Information
Journal of Fluid Mechanics , Volume 42 , Issue 4 , 30 July 1970 , pp. 755 - 768
Copyright
© 1970 Cambridge University Press

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