A finite element thermal analysis of flows with free and moving boundaries.

Industrial processes such as welding and mould casting generally involve fl ows with free surfaces and solid-liquid phase change phenomena. Computation of such processes requires front tracking techniques. For that purpose we have developed an Eulerian finite element model which can deal with both ki nds of interfaces (fluid-fluid, liquid-solid) on unstructured meshes. Then, in order to accurately take into account the material discontinuity throug h the fluid-fluid interface the mesh is locally adapted for the flow comput ation steps. Moreover, this interface mesh fitting allows us to easily incl ude interfacial phenomena such as surface tension or radiative fluxes. On t he other hand, the evolution of the phase change front is undertaken throug h an enthalpy formulation of the heat transfer problem. For most industrial applications, the phase change occurs over a finite temperature range, thu s leading to a mushy region. So no mesh adaptation is required for this sec ond type of interfaces. However, the governing flow equations must be modif ied in order to consider the porous nature of the material in the mushy reg ion. The 2D numerical analysis of an electron beam welding process with our model is presented. (C) Elsevier, Paris.