Yet another hexahedral dominant meshing algorithm: HexDom

In this paper, we describe a robust meshing algorithm for obtaining a mixed mesh with large number of hexahedral/prismatic elements grown over the domain boundary respecting the user imposed anisotropic metric where physics matter the most and in areas where it is required to have the least number of elements. The inner section away from the boundaries is filled with the terminal octants of a non-conformal octree. The remaining unmeshed portion of the domain within the hexahedral/prismatic faces is filled with narrow bands of tetrahedra. The novel idea of the meshing algorithm is the formation of the cavity as slim as possible between the exposed faces of the outer most boundary layers and the octant faces of the inner most terminal octants, in such a way that the length scales of the cavity mesh spacings would allow the frontal tetrahedral meshing algorithm robustly succeeding to fill the cavity respecting its boundary faces without recovery issues. The algorithm could be applied to non-cubical, arbitrary geometries that can also be non-manifold. Each domain region is meshed recursively and within which, the tetrahedral filling algorithm constructs as many manifold cavity shells as the problem constrains are imposed by the boundary layers and the mesh size settings. The final hexahedral dominant mesh is exported to a face-based finite volume format (OpenFoam) so that the non-manifold nature of the mesh is captured by flux based numerical solvers consistently and accurately.