# openmc.cmfd.CMFDMesh¶

class openmc.cmfd.CMFDMesh[source]

A structured Cartesian mesh used for CMFD acceleration.

Variables
• lower_left (Iterable of float) – The lower-left corner of a regular structured mesh. If only two coordinates are given, it is assumed that the mesh is an x-y mesh.

• upper_right (Iterable of float) – The upper-right corner of a regular structured mesh. If only two coordinates are given, it is assumed that the mesh is an x-y mesh.

• dimension (Iterable of int) – The number of mesh cells in each direction for a regular structured mesh.

• width (Iterable of float) – The width of mesh cells in each direction for a regular structured mesh

• energy (Iterable of float) – Energy bins in eV, listed in ascending order (e.g. [0.0, 0.625e-1, 20.0e6]) for CMFD tallies and acceleration. If no energy bins are listed, OpenMC automatically assumes a one energy group calculation over the entire energy range.

• albedo (Iterable of float) – Surface ratio of incoming to outgoing partial currents on global boundary conditions. They are listed in the following order: -x +x -y +y -z +z.

• map (Iterable of int) –

An optional acceleration map can be specified to overlay on the coarse mesh spatial grid. If this option is used, a 0 is used for a non-accelerated region and a 1 is used for an accelerated region. For a simple 4x4 coarse mesh with a 2x2 fuel lattice surrounded by reflector, the map is:

[0, 0, 0, 0,
0, 1, 1, 0,
0, 1, 1, 0,
0, 0, 0, 0]


Therefore a 2x2 system of equations is solved rather than a 4x4. This is extremely important to use in reflectors as neutrons will not contribute to any tallies far away from fission source neutron regions. A 1 must be used to identify any fission source region.

• mesh_type (str) – Type of structured mesh to use. Acceptable values are: * “regular” - Use RegularMesh to define CMFD mesh * “rectilinear” - Use RectilinearMesh to define CMFD

• grid (Iterable of Iterable of float) – Grid used to define RectilinearMesh. First dimension must have length 3 where grid[0], grid[1], and grid[2] correspond to the x-, y-, and z-grids respectively