Using The 3D Tetrahedron Element

Pre-Processing

To provide some assistance for pre-processing with tetrahedral mesh, you may use the 'Gmsh' software (Geuzaine & Remacle, 2022):

• A sample Gmsh input file, which will create tetrahedral mesh within a hexahedral bounding box, can be found here. The program will output a .msh file. Note that this file cannot be directly used as an input in mpm: it must be converted.
• A sample Gmsh output conversion program, compatible with a hexahedral bounding box and the input file mentioned above, can be found here. The conversion program will take a Gmsh output file (note: the .msh must be saved to a .csv before using the converter) and create the following mpm input files:
  • Mesh file (eg. mesh.txt).
  • Entity file (eg. entity_sets.json). Creates a nodal set for each surface of the mesh bounding box.
  • Velocity constraints file (eg. velocity_constraints.txt). Requires inputs of the desired velocity per direction, and per surface of the bounding box.

References

• Geuzaine, C., & Remacle, J. F. (2022). Gmsh (4.9.5) [Computer software]. https://gmsh.info/

Limitations

• The 3D tetrahedron is currently not compatible with MPI.
• Some boundary conditions may not be compatible with the 3D tetrahedron. For details, please see this page.