COMPUTATIONAL MODELLING OF MOULD FILLING IN VERY COMPLEX GEOMETRIES

摘要

The Simulation of shape casting processes involves the simultaneous capture of the rapidly developing metal-air free surface and the liquid-solid moving boundary in the metal phase. Although a wide range of techniques have been developed to address this problem, there are occasions where existing techniques are limited, especially in very complex geometries where the mesh quality may inevitably be relatively poor at some key locations. When conventional cell centred approximations are used on unstructured meshes (such as in conventional CFD tools), then the poor quality cells will inhibit convergence. At this point some detail of the geometry has to be compromised to generate an acceptable mesh upon which the solver will converge. When structured solvers are used then either accuracy has to be compromised to build a mesh that captures most of the geometrical features or the mesh may be very large to reflect all the detail, where much of it is essentially redundant.rnIn this paper we describe an approach to using finite volume discretisation approaches over unstructured meshes (using any combination of element types) where the flow is solved at the cell or element vertex, and all other variables are solved at the cell centre (as in conventional CFD tools). The vertex based flow solver is much more tolerant of meshes with poor quality elements and enables the solution of simultaneous free surface flows coupled with solidification in very complex meshes, thus enabling the capture of such behaviour in arbitrarily complex geometrical structures.