The reconstruction of boundary contours and surfaces in arbitrary unstructured triangular and tetrahedral grids

In an arbitrary assembly of triangles or tetrahedra there is often a requirement to recover or construct edges or triangles which are formed by the connections between nodes. Such is the case in computational methods where grids of triangles or tetrahedra must conform to prespecified boundaries. Discusses general techniques which can be applied to recover edges and triangles within unstructured assemblies of triangles and tetrahedra. The methods described involve the intersection of the required edges and triangles with other nodes, edges, triangles and tetrahedra and then locally performing transformations of the element connectivities. The method is applied to the recovery of fixed boundary triangles for finite element meshes and to the construction of multidomains within unstructured grids. Several applications of the method are given to real practical problems.