Éléments finis stabilisés pour le remplissage en fonderie à haut Reynolds

Abstract : The main objective of this thesis is to develop a complete simulation code for large pieces (up to several meters) metal casting. This kind of processes reveals several coupled physical phenomena and needs adapted numerical methods. Molten metal has usually a low viscosity (around 10-6 m2/s) hence in order to simulate the filling process the use of a turbulence model is required. At the same time, the liquid/air interface must be tracked along with the numerical simulation. In the first part of this work, a stabilized finite element method base on the Variational MultiScale approach (VMS) required for computing the incompressible flows is proposed and analyzed. The latter approach has proved to be efficient in simulating moderate Reynolds numbers, and combined with a convected level-set method, it showed an ability to determine accurately and at any moment the position of the liquid / air interface. Turbulence is taken into account by developing a dynamic Large Eddy Simulation (L.E.S.) model with no empirical data. For validation, each of these methods has been compared to experimental, numerical or analytical results. We also designed our own water flow experimental setting in order to validate our solvers coupling for a representative case. Another feature of these processes having a relatively long duration (over several ten minutes) is the influence of conjugate heat transfers. This can play a major role on the solidification of the metal that is being filled. It is then convenient to develop a stabilized finite element method for convection dominated heat transfer. This method should take into account previously introduced turbulent variables. Finally, we propose an innovative method to simulate the phase change based on a germination/growth approach, with a level-set function. The appliance of all these methods to the moving ice filling case allows the validation of the computational robustness of our code and the well-coupling of its various entities.
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Submitted on : Friday, March 16, 2012 - 10:52:49 AM
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Guillaume François. Éléments finis stabilisés pour le remplissage en fonderie à haut Reynolds. Matériaux. École Nationale Supérieure des Mines de Paris, 2011. Français. ⟨NNT : 2011ENMP0073⟩. ⟨pastel-00679698⟩

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