Tesis doctoral de Angel Heriberto Coppola Owen
Flows with moving interfaces (free surface and two-fluid interface problems) appear in numerous engineering applications. The methods presented in this thesis are oriented mainly to the simulation of mould filling process. Nevertheless the methodology is sufficiently general as to be applied to most free surface and two-fluid interface flows. Numerical modeling provides an efficient way of analyzing the physical phenomena that occur during casting and injection processes. It gives insight into details of the flow that would otherwise be difficult to observe. a fixed mesh finite element method, where the interface position is captured by the level set function, is used. Low froude number flows are particularly challenging for fixed grid methods. An accurate representation is needed in the elements cut by the interface for such flows. Two alternatives are proposed. the first alternative is to use the typical two-phase flow model enriching the pressure shape functions so that the discontinuity in the pressure gradient at the interface can be better approximated. The improvement in the representation of the pressure gradient is shown to be the key to ingredient for the successful modeling of such flows. the influence of the second fluid can be neglected on a wide range of applications to end up with a free surface model that is simpler than the two- phase flow model. The discontinuity in the pressure gradient disappears because only one fluid is simulated. The particularity of this second approach is that a fixed mesh is used. Boundary conditions are applied accurately using enhanced integration and integrating only in the filled part of cut elements. a fixed mesh ale approach is developed to correctly take into account that the domain is moving despite a fixed mesh is used. pressure segregation methods are explored as an alternative to the monolithic discretization of the navier stokes equations. They uncouple the velocity and pressure unknowns, leading to smaller and better conditioned subproblems. Pressure correction and velocity correction methods are presented and compared numerically. Using a discrete laplacian a numerically stable third order velocity correction method is obtained. the methods are applied to three dimensional mould filling problems borrowed directly from the foundry with very satisfactory results. The free surface monolithic model turns out to be the most robust and efficient option. The comparison with a commercial code shows the accuracy and efficiency of the method we propose.
Datos académicos de la tesis doctoral «A finite element model for free surface and two fluid flows on fixed meshes«
- Título de la tesis: A finite element model for free surface and two fluid flows on fixed meshes
- Autor: Angel Heriberto Coppola Owen
- Universidad: Politécnica de catalunya
- Fecha de lectura de la tesis: 19/06/2009
Dirección y tribunal
- Director de la tesis
- Ramón Codina Rovira
- Tribunal
- Presidente del tribunal: sergio Idelson barg
- Álvaro l.g.a. Coutinho (vocal)
- pedro Díez mejía (vocal)
- thierry Coupez (vocal)