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Modélisation de la turbulence atmosphérique en vue de l'étude du chargement aérodynamique des structures soumises aux effets du vent

Abstract : The aim of this thesis is to compute atmospheric turbulent flows in order to study aerodynamic effects induced by the wind on civil engineering structures. A two-dimensional analysis has been carried out to provide a description of the phenomena involved when the wind acts on a bluff body elongated in the across wind direction. In the discussion, the wind has been assumed as an incompressible turbulent flow governed, in the atmospheric boundary layer, by the Navier-Stokes equations. The turbulent stresses have been determined by a first order turbulence model. The key parameters that have been taken into accounts are the surface roughness, the topogaphy, the obstructions and/or the development of large-scale organised vortices. The computational procedure has been performed with a finite-element software, CASTEM 2000, in which some uncommon methodology, like wall-functions based upon roughness length concept, have been incorporated. Validation tests have been performed for well-known pratical cases. The results show that the standard k-epsilon turbulence model is unable to simulate unsteady flows over changing terrains, with organised vortices. The more sophisticated RNG k-epsilon model appears to be more adapted to this kind of complex flows. Therefore, the latter model has been used to improve analytic formulations of buffeting forces. The existing quasi-steady formulation, commonly used in buffeting analysis, shows its limitations in the case of bluff bodies gust entry. A new approach is suggested which includes, through modified admittance functions, the turbulence induced by the structure itself. It has been found that the shape of these functions depends on both the creation of separation bubbles and the formation of vortices in the wake of the body.
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Contributor : Grégory TURBELIN Connect in order to contact the contributor
Submitted on : Tuesday, November 12, 2019 - 3:36:31 PM
Last modification on : Monday, June 29, 2020 - 2:54:04 PM
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Grégory Turbelin. Modélisation de la turbulence atmosphérique en vue de l'étude du chargement aérodynamique des structures soumises aux effets du vent. Mécanique des fluides [physics.class-ph]. Université d'Evry Val d'Essonne, 2000. Français. ⟨tel-02359884⟩



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