Configure a parameter file

ImmersX applications read a deal.II ParameterHandler file. The root dimension and space dimension entries select the statically instantiated problem where an application supports more than one dimension. The input filename never selects the dimension.

Keep parameter files in a repository or build-tree directory and pass the path explicitly:

./build/poisson path/to/poisson.prm

For repository tests, use .prm.in templates under gtests/, tests/, data/, or tutorials/. CMake replaces @IMMERSX_SOURCE_DIR@, @IMMERSX_BINARY_DIR@, @TEST_DATA_DIR@, and @TEST_OUTPUT_DIR@ and writes the generated file below the build tree.

Use the application reference to identify the executable and the API reference for the parameter class behind a section. Tutorials show only the options needed for their example; they are not complete parameter manuals.

Gmsh physical identifiers

For a Gmsh mesh read through Domain, numeric physical tags select material ids on cells and boundary ids on lower-dimensional entities. A physical group does not need a name. Named selectors such as MaterialID:7,ManifoldID:2 or BoundaryID:5,ManifoldID:3 override those defaults. Groups without a physical tag retain id zero.

Some deal.II Gmsh API readers discard unnamed physical tags. ImmersX works around this during import by making only unnamed groups’ numeric ids explicit in a temporary binary MSH 4.1 mesh, then delegating to the same deal.II reader. Binary coordinates retain their precision; export scaling and orphan filtering are disabled for this copy. Named selectors, untagged entities, and the source file remain unchanged. Imports requiring this workaround perform an extra Gmsh read/write; temporary files are removed and the five Gmsh mesh-output settings are restored, including on failure. This protects Domain imports, not direct calls to a separately installed deal.II reader.