stellarmesh 1.0.0b1

Meshing library for nuclear workflows.

Stellarmesh is a meshing library for nuclear workflows. Principally, it supports the creation of DAGMC geometry from CAD models.

Features:

• Import of CadQuery, build123d, STEP and BREP geometry
• Surface and volume meshing
• Gmsh and OpenCASCADE meshing backends
• Linear and angular mesh tolerances
• Imprinting and merging of conformal geometry
• Mesh refinement
• Programatic manipulation of .h5m tags
• Automated testing and integration

Contents

• Contents
• Installation
• Usage
  • Geometry construction
  • Examples
    • Simple torus geometry
    • Other
  • Logging
  • Mesh refinement

Installation

Stellarmesh requires several dependencies that must be installed either from source or from conda-forge. At a minimum, these are moab, python-gmsh, and OCP. However, most users will likely also want build123d for geometry construction and openmc for simulation. See environment.yml for a sample conda environment.

From there, Stellarmesh can be installed from PyPI.

pip install stellarmesh

[!WARNING] While OCP and Gmsh can both be installed from PyPI, they are not ABI compatible. Usage of these packages will result in errors for some geometries.

Usage

For documentation and usage examples, see the examples and tutorials folders.

Geometry construction

Stellarmesh supports both build123d (recommended) and CadQuery for geometry construction but does not depend on either.

The included examples use build123d, which can be installed from conda-forge.

Meshing

Stellarmesh supports surface meshing with both OCC and Gmsh backends.

OCC

The OpenCASCADE (OCC) meshing backend is the preferred backend when linear or angular mesh tolerances are required.

Gmsh

The Gmsh meshing backend offers a number of meshing algorithms for both surface and volume meshes. More detailed documentation, see gmsh.info.

Example

Simple torus geometry

import build123d as bd
import stellarmesh as sm

solids = [bd.Solid.make_torus(1000, 100)]
for _ in range(3):
    solids.append(bd.Solid.thicken(solids[-1].faces()[0], 100))
solids = solids[1:]

geometry = sm.Geometry(solids[::-1], material_names=["a", "a", "c"])
mesh = sm.SurfaceMesh.from_geometry(
    geometry, sm.GmshSurfaceOptions(min_mesh_size=50, max_mesh_size=200)
)
mesh.write("test.msh")
mesh.render("doc/torus-mesh-reversed.png", rotation_xyz=(90, 0, -90), normals=15)

h5m = sm.DAGMCModel.from_mesh(mesh)
h5m.write("dagmc.h5m")
h5m.write("dagmc.vtk")

Rendered mesh with normals.

Check overlaps

❯ overlap_check dagmc.h5m

NOTICE:
     Performing overlap check using triangle vertex locations only.
     Use the '-p' option to check more points on the triangle edges.
     Run '$ overlap_check --help' for more information.

Running overlap check:
100% |===============================================================>|+
No overlaps were found.

Check materials

❯ mbsize -ll dagmc.h5m | grep mat:

NAME = mat:a
NAME = mat:c

Check watertight

❯ check_watertight dagmc.h5m

number of surfaces=4
number of volumes=3

0/0 (nan%) unmatched edges
0/4 (0%) unsealed surfaces
0/3 (0%) unsealed volumes
leaky surface ids=
leaky volume ids=
0.173068 seconds

Other

• Mesh refinement
• Stellarmesh logo
• Imprinted boxes

Logging

Stellarmesh uses the logging library for debug, info and warning messages. Set the level with:

import logging

logging.basicConfig() # Required in Jupyter to correctly set output stream
logging.getLogger("stellarmesh").setLevel(logging.INFO)

Mesh refinement

[!NOTE] Given CAD geometry, Gmsh often produces high-quality meshes that do not benefit from remeshing.

Stellarmesh supports mesh refinement using the mmg library. Refine a mesh with:

refined_mesh = mesh.refine(
  ...
)

and consult the Mesh.refine and mmgs documentations for parameter values.

The refined mesh has more triangles in regions with high curvature thanks to the hausdorff parameter.

Many thanks to Erik B. Knudsen for his work on remeshing for CAD-to-OpenMC.

Acknowledgements

Stellarmesh is originally a project of Thea Energy, who are building the world's first planar coil stellarator.