Compatible Model Grids
VRGIDns is a NASA Langley developed grid generator which produces high quality stretched meshes suitable for Navier-Stokes calculations. VRGIDns produces fully tetrahedral meshes exclusively. However, VRGIDns also produces a *.poin1 file which can be used to identify the structure of the tetrahedra in the viscous regions.
The relevant output files from VGRIDns for the NSU3D package are:
ugform is used to reformat the *.cosgs and *.bc VGRIDns grid files into a *.cell file. This *.cell file describes a fully tetrahedral mesh. The mesh merging operation is then performed in two phases, first by running this *.cell file and the VGRIDns *.poin1 file through the merge1 program, and then running the result produced by this procedure through the merge2 program, which produces a new *.cell file, which now corresponds to a mixed prismatic/tetrahedral mesh, which usually also contains a small number of pyramids. This new *.cell file is now used as the basis for all subsequent pre- and post-processing operations in the NSU3D package. The *.poin1 file is also required as input to the amg3d agglomeration multigrid pre-processing program, and therefore should not be discarded.
ICEM Tetra grids can be output directly in the *.cell format for nsu3d, by selecting the NSU3D output option. However, these are labeled as *.bin upon output from ICEM Tetra. These are probably best relabeled with a *.cell suffix. Since ICEM Tetra can produce mixed prismatic- tetrahedral grids directly, there is no need for a merging process. However, ICEM Tetra does not produce a *.poin1 file. A separate facility called makepoin1 is available for reconstructing this file, since it is required by the amg3d agglomeration multigrid pre-processor.