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Modélisation d'écoulements atmosphériques stratifiés par Large-Eddy Simulation à l'aide de Code_Saturne

Abstract : Large-eddy simulation (LES) of the physical processes in the atmospheric boundary layer (ABL) remains a complex subject. LES models have difficulties to capture the evolution of the turbulence in different conditions of stratification. Consequently, LES of the whole diurnal cycle of the ABL including convetive situations in daytime and stable situations in the night time is seldom documented. The simulation of the stable atmospheric boundary layer which is characterized by small eddies and by weak and sporadic turbulence is espacialy difficult. Therefore The LES ability to well reproduce real meteorological conditions, particularly in stable situations, is studied with the CFD code developed by EDF R&D, Code_Saturne. The first study consist in validate LES on a quasi-steady state convective case with homogeneous terrain. The influence of the subgrid-scale models (Smagorinsky model, Germano-Lilly model, Wong-Lilly model and Wall-Adapting Local Eddy-viscosity model) and the sensitivity to the parametrization method on the mean fields, flux and variances are discussed.In a second study, the diurnal cycle of the ABL during Wangara experiment is simulated. The deviation from the measurement is weak during the day, so this work is focused on the difficulties met during the night to simulate the stable atmospheric boundary layer. The impact of the different subgrid-scale models and the sensitivity to the Smagorinsky constant are been analysed. By coupling radiative forcing with LES, the consequences of infra-red and solar radiation on the nocturnal low level jet and on thermal gradient, close to the surface, are exposed. More, enhancement of the domain resolution to the turbulence intensity and the strong atmospheric stability during the Wangara experiment are analysed. Finally, a study of the numerical oscillations inherent to Code_Saturne is realized in order to decrease their effects
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https://pastel.archives-ouvertes.fr/pastel-00861196
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Submitted on : Thursday, September 12, 2013 - 10:48:13 AM
Last modification on : Thursday, October 17, 2019 - 9:40:04 PM
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Cédric Dall'Ozzo. Modélisation d'écoulements atmosphériques stratifiés par Large-Eddy Simulation à l'aide de Code_Saturne. Sciences de la Terre. Université Paris-Est, 2013. Français. ⟨NNT : 2013PEST1026⟩. ⟨pastel-00861196⟩

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