Heat convection in a vertical channel : Plumes versus turbulent diffusion

Mathieu Gibert (1) , Hervé Pabiou (1) , Jean-Christophe Tisserand (1) , Betina B. Gertjerenken (1) , Bernard Castaing (1) , Francesca Chillà (1)

1 Phys-ENS - Laboratoire de Physique de l'ENS Lyon

Following a previous study [Gibert , Phys. Rev. Lett. 96, 084501 (2006)], convective heat transfer in a vertical channel of moderate dimensions follows purely inertial laws. It would be therefore a good model for convective flows of stars and ocean. Here we report new measurements on this system. We use an intrinsic length in the definition of the characteristic Rayleigh and Reynolds numbers. We explicit the relation between this intrinsic length and the thermal correlation length. Using particle imaging velocimetry, we show that the flow undergoes irregular reversals. We measure the average velocity profiles and the Reynolds stress tensor components. The momentum flux toward the vertical walls seems negligible compared to the shear turbulent stress. A mixing length theory seems adequate to describe the horizontal turbulent heat and momentum fluxes, but fails for the vertical ones. We propose a naive model for vertical heat transport inspired by the Knudsen regime in gases.

Mots clés: Turbulent thermal convection; Thermal plumes; Turbulent diffusion; Rayleigh Benard Convection; Particle image velocimetry

Domaines: Dynamique des Fluides [physics.flu-dyn]; Mécanique des fluides [physics.class-ph]; Mécanique des fluides [physics.class-ph]; Physique Atmosphérique et Océanique [physics.ao-ph]; Géophysique [physics.geo-ph]; Géophysique [physics.geo-ph]; Autre [cond-mat.other]; Milieux et Changements globaux

Mathieu Gibert, Hervé Pabiou, Jean-Christophe Tisserand, Betina B. Gertjerenken, Bernard Castaing, et al.. Heat convection in a vertical channel : Plumes versus turbulent diffusion. Physics of Fluids, 2009, 21 (3), pp.035109. ⟨10.1063/1.3085812⟩. ⟨ensl-00377244⟩