Prandtl and Rayleigh numbers dependences in Rayleigh-Bénard convection

Using low-temperature gaseous helium close to the critical point, we investigate the Prandtl-number dependence of the effective heat conductivity (Nusselt number) for a 1/2 aspect ratio Rayleigh-Bénard cell. Very weak dependence is observed in the range 0.7 < Pr < 21; 2 × 10^8 < Ra < 2 ×...

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Bibliographic Details
Published in:Europhysics letters 2002-06, Vol.58 (5), p.693-698
Main Authors: Roche, P.-E, Castaing, B, Chabaud, B, Hébral, B
Format: Article
Language:English
Subjects:
Buoyancy-driven instability
Condensed Matter
Condensed matter: structure, mechanical and thermal properties
Engineering Sciences
Exact sciences and technology
Fluid Dynamics
Fluid mechanics
Fluids mechanics
Fundamental areas of phenomenology (including applications)
Hydrodynamic stability
Mechanics
Other
Other topics in quantum fluids and solids
liquid and solid helium
Physics
Quantum fluids and solids
liquid and solid helium
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Summary:Using low-temperature gaseous helium close to the critical point, we investigate the Prandtl-number dependence of the effective heat conductivity (Nusselt number) for a 1/2 aspect ratio Rayleigh-Bénard cell. Very weak dependence is observed in the range 0.7 < Pr < 21; 2 × 10^8 < Ra < 2 × 10^10: the absolute value of the average logarithmic slope δ = (∂ln Nu/∂ln Pr)Ra is smaller than 0.03. A bimodality of Nu, with 7% difference between the two sets of data, is observed, which could explain some discrepancies between precise previous experiments in this range.
ISSN:0295-5075
1286-4854
DOI:10.1209/epl/i2002-00405-1