Convection thermique : transport et mélange

Abstract : During this thesis, we have studied turbulent thermal convection. This manuscript can be divided in three parts. In the first part, we have studied the influence of roughness on the efficiency of thermal transport in a cylindrical and in a rectangular Rayleigh Benard cell. Thanks to thermal measurements, we have observed a transition when the thickness of the thermal boundary layer is equal to the characteristic height of the roughness. After the transition, a new convective regime appears. We purpose here a model which accounts for these observations. In a second part, we have studied turbulent thermal convection in a vertical long channel. In this configuration, PIV measurements unveil that the mean flow can be divided in two columns : either the hot water goes up at the right side et the cold water goes down at the left side or the opposite. Furthermore, we have analyzed the influence of the power on the mean flow at once for the long times (time reversals of the columns) and for the short times (mean velocity profiles, fluctuations measurements and thermal plumes velocity) In a third part, a second free parameter is included : the tilted angle. PIV experiments and thermal measurements allowed us to study the competition between turbulence and stratification in the tilted long channel. A model which explains turbulent measurements is developed.
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Submitted on : Monday, August 1, 2011 - 10:07:48 PM
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Jean-Christophe Tisserand. Convection thermique : transport et mélange. Dynamique des Fluides [physics.flu-dyn]. Ecole normale supérieure de lyon - ENS LYON, 2010. Français. ⟨tel-00612953⟩

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