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Effet de la convection naturelle et forcée lors des transitions de phases : Application à la croissance cristalline

Abstract : This work concerns the influence of natural convection during solid-liquid phase change. The geometrical configuration considered throughout this study was chosen to correspond to the crucible of the 'Afrodite' benchmark experiment. Various numerical models (3D, 2D and 2D1/2) have been proposed to study cases of natural convection, pure materials's solid-liquid phase change and solidification of metallic alloys involving segregation phenomena. The classical 2D models, which do not take into account the viscous dissipation induced by the side walls of the crucible, are shown to be unable to predict reliable results. The proposed 2D1/2 models are obtained by averaging momentum, energy and heat conservation equations along the short transverse direction, assuming adjustable transverse velocity profiles depending on a parameter δ. A validity domain where these models are applicable is rigorously defined in terms of ranges of variation of the control parameters. An empirical expression is also proposed for the optimal δ values, for which the 2D1/2 models can accurately replace the 3D models for both natural convection problems (flow intensity and temperature fields) and pure materials solid-liquid phase change cases (form and evolution of the liquid solid-liquid front). The multi-domain approach, used for pure materials solid-liquid phase change cases, and the enthalpy approach coupled with a segregation model, used for binary metallic alloys solidification cases, are detailed. A comparison between the numerical results, obtained with the 2D1/2 model, and the experimental results, obtained with the 'Afrodite' benchmark, for the solidification of both pure tin and tin-lead ingots, is carried out. Special care has been devoted to the definition of the boundary conditions that are representative of the experiments. A good agreement is finally found between the numerical and experimental results.
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Submitted on : Friday, July 17, 2020 - 6:33:09 PM
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Idir Hamzaoui. Effet de la convection naturelle et forcée lors des transitions de phases : Application à la croissance cristalline. Mécanique des fluides [physics.class-ph]. Université de Lyon; Université des sciences et de la technologie Houari Boumediene (Alger), 2019. Français. ⟨NNT : 2019LYSEI132⟩. ⟨tel-02902123⟩

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