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Heat-flux transitions at low Rayleigh number

Published online by Cambridge University Press:  29 March 2006

Wendell Brown
Wendell Brown
Affiliation:
Department of Meteorology, Massachusetts Institute of Technology Present address: Institute of Geophysics and Planetary Physics, University of California, La Jolla, California 92037.
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Abstract

The transition to turbulence in the convective flow of air between horizontal plates in a circular convection chamber has been investigated. Measurements of the heat flux and the instantaneous spatial temperature field were made simultaneously for a range of Rayleigh number Ra between 3 × 103 and 5 × 104. Ra could be varied by changing the vertical separation or the temperature difference between the plates. The temperature field was measured with either a horizontal or a vertical array of resistance wires mounted so that the flow field could be traversed at velocities much greater than flow velocities characteristic of thermal convection. Slope transitions in the heat flux were found at Ra = 9600 and Ra = 26000. Many measurements of the instantaneous horizontal distribution of temperature for Ra > RaT2 indicate a growth in amplitude of fluctuations with non-dimensional cyclical wavenumbers of 0·4 and greater. The probability of observing these high wavenumber fluctuations also increases as Ra becomes greater than RaT2. The horizontal wavelengths of the different types of temperature fluctuations are compared with the observations of others.

Type
Research Article
Information
Journal of Fluid Mechanics , Volume 60 , Issue 3 , 18 September 1973 , pp. 539 - 559
Copyright
© 1973 Cambridge University Press

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