Automated Hexahedral Mesh Generation by Virtual Decomposition

Mapping and sweeping mesh generating algorithms are some of the most common methods used for the creation of hexahedral meshes. These algorithms quickly generate high quality elements; however, they typically require manual decomposition of the geometry into regular primitive pieces. Two CUBIT meshing facilitators, volume submapping and n-surface sweeping, have been designed to greatly reduce the need for manual decomposition and the propagation of these cuts throughout the model, while generating high-quality hexahedral elements. This paper will focus on the implementation and capabilities of volume submapping while briefly discussing n-surface sweeping. Volume submapping uses pseudo or virtual geometry to decompose complex volumes into “mappable sub-volumes.” Mappable regions are generally limited to volumes that can be parameterized into logical hexahedrals. To decompose volumes into mappable “subvolumes”, the mesh connectivity of the surfaces bounding the solid is used to parameterize the surface nodes in a local integer “i-j-k” space. This parameterization provides the information for decomposition of the volume by the creation of virtual surfaces inside the volume. The virtual surfaces separate the volume into mappable “sub-volumes”. Because the virtual surfaces have no underlying geometry, the resulting hexahedral mesh can be smoothed to eliminate the “sharpness” of the decomposition surfaces or to increase the conformity of the mesh to the original geometry. This process reduces the need for manual geometry decomposition, a time consuming and often difficult manual task. This process is not generally applicable to all geometries. However, the process, does reduce the need for manual decomposition of a large class of realistic solid models with the benefits of reduced time and complexity of the meshing process. Current work in the n-surface sweeping development involves improving the CUBIT sweep tool to allow multiple source surfaces to be projected to a single target surface. The n-surface sweeping is based on existing CUBIT features. * This work performed at Sandia National Laboratories supported by the US Dept. of Energy under contract number DE--AC04--94AL85000.