Generating Massive Unstructured Meshes for OpenFOAM

Abstract: OpenFOAM is an open source computational fluid dynamics (CFD) package with a large user base from many areas of engineering and science. This whitepaper documents an enablement tool called PMSH that was developed to generate multi-billion element unstructured tetrahedral meshes for OpenFOAM. PMSH is developed as a wrapper code around the popular open source sequential Netgen mesh generator. Parallelization of the mesh generation process is carried out in five main stages: (i) generation of a coarse volume mesh (ii) partitioning of the coarse mesh to get sub-meshes, each of which is processed by a processor (iii) extraction and refinement of coarse surface sub-meshes to produce fine surface sub-meshes (iv) re-meshing of each fine surface sub-mesh to get the final fine volume mesh (v) matching of partition boundary vertices followed by global vertex numbering. An integer based barycentric coordinate method is developed for matching distributed partition boundary vertices. This method does not have precision related problems of floating point coordinate based vertex matching. Test results obtained on an SGI Altix ICE X system with 8192 cores and 14 TB of total memory confirm that our approach does indeed enable us to generate multi-billion element meshes in a scalable way. PMSH tool is available at