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Convection compressible : expériences en hypergravité et modélisation anélastique quasi-géostrophique

Abstract : In large natural objects, thermal convection is associated with large pressure differences, mainly due to hydrostatic balance. This is true in the atmosphere of the Earth (and other planets), in gas giant planets, in stars, but also in the interior of telluric planets. Boussinesq approximation is not valid owing to large compressibility effects, and other approximate models can be used to model these objects, like the anelastic approximation. However, very few experiments have been performed to assess these models. In the present PhD thesis, an experiment is shown, with parameters designed to maximize compressibility effects in a laboratory. In this perspective, an enhanced apparent gravity is obtained using a centrifuge, and Xenon gas is used, allowing us to reach a significant dissipation parameter. In our experiments, we have observed an adiabatic gradient of 3~K/cm and the power law between the superadiabatic Rayleigh number and the Nusselt number measuring the turbulent heat transfer is characterized by an exponent 0.3.Measurements of temperature and pressure fluctuations show that the flow is quasi-geostrophic as a result of the strong rotation rate of the centrifuge. An anelastic, quasi-geostrophic model has then been developed and solved numerically in the same configuration as the experiments.
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Submitted on : Tuesday, October 29, 2019 - 4:38:03 PM
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Rémi Menaut. Convection compressible : expériences en hypergravité et modélisation anélastique quasi-géostrophique. Sciences de la Terre. Université de Lyon, 2019. Français. ⟨NNT : 2019LYSEN023⟩. ⟨tel-02337874⟩

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