Package: cad-to-h5m
This is a minimal Python package that provides bothcommand lineandAPIinterfaces for convertingmultipleCAD files (STP and SAT format)
into a DAGMC h5m file using the Cubit Python API.This is useful for creating the DAGMC geometry for use in compatible neutronics
codes such as OpenMC, FLUKA and MCNP.The geometry is tagged wih material names, optional imprinted and merging
during the process which can speed up particle transport.InstallationThe package is available via the PyPi package manager and the recommended
method of installing is via pip.pipinstallcad_to_h5mIn additionCubitand theSvalinn Pluginneeds to be
installed to make full use of this package.Python API usageCreating a h5m file from a single STP file calledpart1.stpand applying
a material tag to the volume.fromcad_to_h5mimportcad_to_h5mcad_to_h5m(files_with_tags=[{'cad_filename':'part1.stp','material_tag':'m1'}],h5m_filename='dagmc.h5m',cubit_path='/opt/Coreform-Cubit-2021.5/bin/')Creating a h5m file from two STP files calledpart1.stpandpart2.stp.
Both parts have distinct material tag applied to them and the result is output
as a h5m file with the filename dagmc.h5m.fromcad_to_h5mimportcad_to_h5mcad_to_h5m(files_with_tags=[{'cad_filename':'part1.stp','material_tag':'m1'},{'cad_filename':'part2.stp','material_tag':'m2'}],h5m_filename='dagmc.h5m',cubit_path='/opt/Coreform-Cubit-2021.5/bin/')Creating a h5m file from a single SAT is a similar process. Note the .sat file
extension.fromcad_to_h5mimportcad_to_h5mcad_to_h5m(files_with_tags=[{'cad_filename':'part1.sat','material_tag':'m1'}],h5m_filename='dagmc.h5m',cubit_path='/opt/Coreform-Cubit-2021.5/bin/')Creating a tet mesh files compatible with the OpenMC / DAGMC Unstructured mesh
format is also possible. Another key calledtet_meshto thefiles_with_tagsdictionary will trigger the meshing of that CAD file.
The value of the key will be passed to the Cubit mesh command as an instruction.
The following command will produce aunstructured_mesh_file.exofile that can then be used in DAGMC compatible neutronics codes. There are examples12for the use of unstructured meshes in OpenMC.fromcad_to_h5mimportcad_to_h5mcad_to_h5m(files_with_tags=[{'cad_filename':'part1.sat','material_tag':'m1','tet_mesh':'size 0.5'}],h5m_filename='dagmc.h5m',cubit_path='/opt/Coreform-Cubit-2021.5/bin/'exo_filename='unstructured_mesh_file.exo')Use ifexofiles requires OpenMC to be compiled with LibMesh. OpenMC also
accepts DAGMC tet meshes made with MOAB which is another option. The following
example creates acubfile that contains a mesh. The MOAB toolmbconvertis then used to extract the tet mesh and save it as ah5mfile which cna be used in OpenMC as shown in the OpenMCexamplesfromcad_to_h5mimportcad_to_h5mcad_to_h5m(files_with_tags=[{'cad_filename':'part1.sat','material_tag':'m1','tet_mesh':'size 0.5'}],h5m_filename='dagmc.h5m',cubit_path='/opt/Coreform-Cubit-2021.5/bin/',cubit_filename='unstructured_mesh_file.cub')Thecubfile produced contains a tet mesh as well as the faceted geometry.
The tet mesh can be extracted and converted to anotherh5mfile for use in
OpenMC. MOAB is needed to convert the file and includes the command line toolmbconvert, MOAB can be installed into a Conda environment with:conda install -c conda-forge moabThenmbconvertcan be used to extract and convert the tet mesh from thecubfile into ah5mfile.mbconvertunstructured_mesh_file.cubunstructured_mesh_file.h5mScaling geometry is also possible. This is useful as particle transport codes
often make use of cm as the default unit. CAD files typically appear in mm as
the default limit. Some CAD packages ignore units while others make use of them.
The h5m files are assumed to be in cm by particle transport codes so often it
is necessary to scale up or down the geometry. This can be done by adding
another key calledscaleand a value to thefiles_with_tagsdictionary. This example multiplies the geometry by 10.fromcad_to_h5mimportcad_to_h5mcad_to_h5m(files_with_tags=[{'cad_filename':'part1.sat','material_tag':'m1','scale':10}],h5m_filename='dagmc.h5m',)Assigning a material to the implicit complement is also possible. This can be useful on large complex geometries where boolean operations can result in robustness issues. This is implemented by assigning the desired material tag of the implicit complement to the optionalimplicit_complement_material_tagargument. Defaults to vacuum.fromcad_to_h5mimportcad_to_h5mcad_to_h5m(files_with_tags=[{'cad_filename':'part1.sat','material_tag':'m1',}],h5m_filename='dagmc.h5m',implicit_complement_material_tag='m2')