Turbulent Rayleigh–Bénard convection in gaseous and liquid He

In this article we deal with the turbulent regimes of Rayleigh–Bénard convection, namely the 2/7 regime and beyond. An experiment with He at low temperature allows us to explore a large Rayleigh number (Ra) range up to 2×10 14 , under Boussinesq conditions, while the Prandtl number (Pr) is equal to...

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Bibliographic Details
Published in:Physics of fluids (1994) 2001-05, Vol.13 (5), p.1300-1320
Main Authors: Chavanne, X., Chillà, F., Chabaud, B., Castaing, B., Hébral, B.
Format: Article
Language:English
Subjects:
Boundary layers
Heat convection
Laminar flow
Prandtl number
Superfluid helium
Thermometers
Transition flow
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Summary:In this article we deal with the turbulent regimes of Rayleigh–Bénard convection, namely the 2/7 regime and beyond. An experiment with He at low temperature allows us to explore a large Rayleigh number (Ra) range up to 2×10 14 , under Boussinesq conditions, while the Prandtl number (Pr) is equal to and larger than 0.7. Calorimetric measurements evidence a departure from the 2/7 regime above Ra =10 11 toward a new regime where the heat transfer is enhanced. Local measurements with two nearby thermometers allows us to relate this change to a laminar–turbulent transition of the velocity boundary layer induced by the large-scale flow near the walls of the cell. The features of the observed new regime match those of the ultimate regime predicted by R. Kraichnan [Phys. Fluids 5, 1374 (1962)] at moderate Pr; in particular, our experimental data show that the thermal boundary layer lies inside the viscous sublayer of the turbulent boundary layer.
ISSN:1070-6631
1089-7666
DOI:10.1063/1.1355683