The onset and development of flow in a thick horizontal layer subject to a near-constant flux heating from below has been studied experimentally. The overall heat-flux-based Rayleigh number, Ra*, ranges from 2 × 108 to 7 × 1010. Flow visualization shows the growth and breakdown of a conduction layer adjacent to the heated surface. Convection is characterized by the release of warm meandering plumes and thermals from a boundary layer. The planform of convection at the heated surface begins with a pattern of small spots suggestive of Be´nard cells. Some of these cells expand, forming a larger cell pattern. This continues until a quasi-steady state is reached in which the former cell boundaries form a slowly moving pattern of warm lines on the heated surface. The lines are believed to be the source of the plumes and thermals. Quantitatively, the onset of convection occurs at a constant (critical) Rayleigh number based on the conduction layer thickness, Raδ. Based on the first observation of fluid motion, this critical Rayleigh number is approximately 1300. Based on the heated surface temperature the critical Rayleigh number is 2700. The nondimensional wavenumber associated with the observed instabilities at the onset of convection is about 2.2.
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Onset and Development of Natural Convection Above a Suddenly Heated Horizontal Surface
R. J. Goldstein,
R. J. Goldstein
Department of Mechanical Engineering, University of Minnesota, Minneapolis, MN 55455
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R. J. Volino
R. J. Volino
Department of Mechanical Engineering, University of Minnesota, Minneapolis, MN 55455
Search for other works by this author on:
R. J. Goldstein
Department of Mechanical Engineering, University of Minnesota, Minneapolis, MN 55455
R. J. Volino
Department of Mechanical Engineering, University of Minnesota, Minneapolis, MN 55455
J. Heat Transfer. Nov 1995, 117(4): 808-821 (14 pages)
Published Online: November 1, 1995
Article history
Received:
October 1, 1994
Revised:
April 1, 1995
Online:
January 23, 2008
Citation
Goldstein, R. J., and Volino, R. J. (November 1, 1995). "Onset and Development of Natural Convection Above a Suddenly Heated Horizontal Surface." ASME. J. Heat Transfer. November 1995; 117(4): 808–821. https://doi.org/10.1115/1.2836296
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