Especially for complex geometries with non trivial domain decomposition, a visualization of cell volumes, cell surfaces and the domain decomposition can be helpful for debugging purposes.

Therefore the following files are regularly created upon each start of a simulation case:

`domain_decomposition.pos`

- Visualization of the volume segment structure. In GMSH this can be best viewed when merged together with the MSH file of the geometric model. An example for a domain decomposition plot is given in 3D gas flow - optimized domain decomposition.`cell_volume.pos`

- Effective cell volume per cell. Cells within solid walls should have zero volume. Cells within the free gas volume should have a volume according to their dimension (length, width, height, ). Cells partially intersecting with a solid wall should have a smaller volume depending on the intersection fraction.`cell_surfaces.pos`

- Effective surface of intersecting walls. This should be only non-zero for cells, which are partially intersecting with a wall. For walls which are located*exactly*between two cells, at least one of both cells should show the effective wall surface.

If e.g. the `cell_volumes.pos`

plot shows non-zero volume, where a solid wall is expected, this gives a hint about possible mistakes in the geometric model such as a missing or doubly selected single surface.

**Postprocessing**-