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Convection thermique turbulente : Panaches et Fluctuations

Abstract : In this study we investigate the phenomenon of thermal turbulent convection in new and unprecedented ways.

The first system we studied experimentally is an « infinite » vertical channel, where a constant vertical mean gradient of temperature exists. Inside this channel the average mass flux is null. The results obtained from our measurements reveal that the flow is mainly inertial; indeed the dissipative coefficients (here the viscosity) play a role only to define a coherence length L. This length is the distance over which the thermal plumes can be considered as « free falling » objects. The horizontal transport, of heat and momentum, is entirely due to fluctuations. The associated « mixing length » is small compared to the channel width. In the other hand, the vertical heat transport is due to coherent structures: the heat plumes.
Those objects were also investigated in a Lagrangian study of the flow in the bulk of a Rayleigh-Bénard cell. The probe, which has the same density as the fluid used in this experiment, is a sphere of 2 cm in diameter with embarked thermometers and radio-emitter. The heat plumes transport it, which allows a statistical study of such objects.
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https://tel.archives-ouvertes.fr/tel-00268361
Contributor : Mathieu Gibert <>
Submitted on : Monday, March 31, 2008 - 6:28:01 PM
Last modification on : Wednesday, November 20, 2019 - 2:38:56 AM
Long-term archiving on: : Thursday, May 20, 2010 - 10:44:55 PM

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  • HAL Id : tel-00268361, version 1

Citation

Mathieu Gibert. Convection thermique turbulente : Panaches et Fluctuations. Dynamique des Fluides [physics.flu-dyn]. Ecole normale supérieure de lyon - ENS LYON, 2007. Français. ⟨tel-00268361⟩

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