Turbulent convection in Rayleigh-Bénard cells with modified boundary conditions

Abstract : The present document is dedicated to the study of the large-scale flow patterns in turbulent Rayleigh-Bénard convection, and of the influence exerted by different factors on the flow structures and on their temporal evolution. This work is composed of three parts. In the first part, we study the structure and the temporal evolution of the large-scale flow inside a square (2D) Rayleigh-Bénard cell. The proposed characterization combines a statistical analysis with a physical approach relying on the angular momentum as well as the kinetic and potential energies to highlight the underlying physical mechanisms. We subsequently attempt to tie these mechanisms together to each of the distinctive flow patterns observed and to their temporal evolution. In the second part, we focus on the changes in the large-scale flow resulting from imposing a stress-free surface on a square (2D) Rayleigh-Bénard cell, thus breaking the top/bottom symmetry. This configuration exhibits a lower bulk temperature, enhanced heat-flux and increased fluctuations with respect to the classical case. In the last part, we focus on the changes in the large-scale flow resulting from imposing a strong degree of lateral confinement on a slim rectangular (3D) Rayleigh-Bénard cell. This configuration exhibits the formation of large coherent structures in the vertical direction, or turbulent channels, instead of a system-wide circulation. Confinement also exhibits a strong influence on several global quantities such as the Nusselt and Reynolds numbers. In order to assist in the exploration of the severely confined regime, we develop and validate a reduced dimensionality model with inertial corrections. Using this model, we are able to explore the parameter space and provide further insight in the limit of strong confinement. Except where otherwise noted this work is licensed under https://creativecommons.org/licenses/by-nc-nd/3.0/
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https://hal.sorbonne-universite.fr/tel-01609741
Contributor : Andrés Castillo-Castellanos <>
Submitted on : Tuesday, October 3, 2017 - 10:45:40 PM
Last modification on : Thursday, March 14, 2019 - 9:56:03 PM

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Andres Castillo-Castellanos. Turbulent convection in Rayleigh-Bénard cells with modified boundary conditions. Fluids mechanics [physics.class-ph]. Université Pierre et Marie Curie - Paris VI, 2017. English. ⟨tel-01609741v1⟩

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