Data Structures and Mesh Modification Tools for Unstructured Multigrid Adaptive Techniques

A complete set of data structures and mesh modification tools for effectively defining unstructured three-dimensional multigrids on general curved domains is presented. The mesh adaptive procedures can be used for generating hierarchies of unstructured grids by means of uniform or local refinement and coarsening, while a local retriagulation algorithm is used for controlling the degradation of the quality of the mesh during adaptation. Intergrid transfer operators are efficiently realized 'on the fly' during adaptation. The data structure allows the efficient storage and handling of multiple grids, where mesh entities belonging to multiple levels can be stored just once. The capabilities and performance of the proposed procedures are exemplified by means of examples.