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On Howard's upper bound for heat transport by turbulent convection

Published online by Cambridge University Press:  29 March 2006

F. H. Busse
Affiliation:
Max-Planck-Institut für Physik und Astrophysik, Munich

Abstract

The variational problem introduced by Howard (1963) for the derivation of an upper bound on heat transport by convection in a layer heated from below is analyzed for the case in which the equation of continuity is added as constraint for the velocity field. Howard's conjecture that the maximizing solution of the Euler equations is characterized by a single horizontal wave-number is shown to be true only for a limited range of the Rayleigh number, Ra. A new class of solutions with a multiple boundary-layer structure is derived. The upper bound for the Nusselt number, Nu, given by these solutions is Nu ≤ (Ra/1035)½ in the limit when the Rayleigh number tends to infinity. The comparison of the maximizing solution with experimental observations by Malkus (1954a) and Deardorff & Willis (1967) emphasizes the similarity pointed out by Howard.

Type
Research Article
Copyright
© 1969 Cambridge University Press

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References

Busse, F. H. 1967a J. Math. Phys. 46, 140.
Busse, F. H. 1967b J. Fluid Mech. 30, 625.
Busse, F. H. 1968 Report MPI/Astro 8/68 (Max-Planck-Institut für Physik und Astrophysik, Munich).
Busse, F. H. 1969 Z. angew. Math. Phys. 20, 1.
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Malkus, W. V. R. 1954b Proc. Roy. Soc. A 225, 196.
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