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Speakle measurements of convection in a liquid cooled from above

Published online by Cambridge University Press:  21 April 2006

R. Meynart ,
P. G. Simpkins  and
T. D. Dudderar
R. Meynart
Affiliation:
Service des Milieux Continus, Université Libre de Bruxelles, Belgium Present address: ACEC, 6000 Charleroi, Belgium.
P. G. Simpkins
Affiliation:
AT&T Bell Laboratories, Murray Hill, NJ 07974, USA
T. D. Dudderar
Affiliation:
AT&T Bell Laboratories, Murray Hill, NJ 07974, USA
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Abstract

Buoyancy-driven recirculation in a liquid-filled rectangular cavity cooled from above is shown to be locally modulated by an unstable thermal layer at the surface. Interferometric observations suggest that fluctuations that occur in a plume descending through the upper liquid layers are of the type described by Howard (1964) and by Krishnamurti & Howard (1981). Temperature measurements across the surface layer are in reasonable agreement with the diffusive heat-conduction model, but indicate that near the plume the fluid is cooler than elsewhere. Quasi-steady measurements of the velocity distribution in the upper regions of the cavity were made using multiple-exposure laser speckle velocimetry. Interrogation of the specklegrams with a Young's fringe technique yields a velocity-vector field of about two thousand elements. These data are used to calculate the corresponding velocity components and estimates of the vorticity distribution. The results compare favourably with measurements recorded directly from Fourier filtering methods.

Type
Research Article
Information
Journal of Fluid Mechanics , Volume 182 , September 1987 , pp. 235 - 254
Copyright
© 1987 Cambridge University Press

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