This repository contains a Python script that turns a 2D tetrahedral GMSH mesh file (MSH version 2) into a set of mesh files that contain important information for a finite-volume code (owner cells, neighbor cells, and other connectivity information). Note that the script is quite rough as I wrote it quickly in the development of a finite-volume code. It is unoptimized and messy but works for now. I will continually improve it whenever I find a chance. Note that currently only MSH version 2 is supported. I found out the hard way that MSH version 4 is problematic and have not found a solution to that yet. Support for 3D and other mesh primitives should come soon.
The package gmsh must be installed to enable GMSH Python API.
python3 convert_gmsh_fvm.py [input .msh file]
Three files will be generated in mesh/ (make sure this directory is available): node, face, cell which contains information for mesh nodes, faces, and cells, respectively.
All indices in the output files are 1-based. If you use a 0-based indexing system in your code, make sure to correct for this. If an index in the output file is -1 that means the corresponding entity does not exist. For example, a boundary face does not have a neighbor cell; therefore, neighbor_cell_idx is -1.
The first line contains the number of nodes n_nodes. The next n_nodes lines contain node information.
number of nodes
x y z coordinates
...
The first line contains the number of faces n_faces. The next n_faces lines contain face information.
number of faces
node_1_idx node_2_idx physical_group_idx owner_cell_idx neighbor_cell_idx
...
The first line contains the number of cells n_cells. The next n_cells lines contain cell information.
number of cells
node_1_idx node_2_idx node_3_idx face_1_idx face_2_idx face_3_idx face_1_assoc_neighbor_cell_idx face_2_assoc_neighbor_cell_idx face_3_assoc_neighbor_cell_idx
...