MeshDiagnosticsGenerator

Element volume check

Turn this check on with the "examine_element_volumes" parameter.

A minimum and a maximum element volume can be specified to the MeshDiagnosticsGenerator using the "minimum_element_volumes" and the "maximum_element_volumes" parameters. These diagnostics are mostly used to detect zero or negative volume elements, from distorted meshes.

Side planarity check

Turn this check on with the "examine_nonplanar_sides" parameter.

Non-planar elements are generally supported in MOOSE. However, the ray-tracing capabilities treat them approximately at the moment, so it may be useful to examine the mesh before use.

Subdomain element types check

Turn this check on with the "examine_element_types" parameter.

The Exodus output format only supports a single element type (TRI3, QUAD4, HEX8, HEX20, etc) per subdomain. Rather than erroring at the time of output, this diagnostic outputs which subdomains present multiple element types.

Sideset orientation check

Turn this check on with the "examine_sidesets_orientation" parameter.

Sidesets are oriented. They are represented in MOOSE by a list of elements and sides. Along the boundary, the orientation of these sides should in general be consistent. If it is not, the normal of the sideset is essentially reversed from one side to the next in the sideset.

The sideset orientation check is a heuristic for a common error case. The sideset orientation is only checked for sides that are delimiting two different subdomains. The check makes sure that the order of the subdomains, e.g. which one owns the element and which one owns the element on the other side of the side (the neighbor), does not change throughout the sideset.

Element overlap checks

Turn this check on with the "examine_element_overlap" parameter.

Overlap between elements are generally undesirable. Overlapping elements can be associated with non-conformality and/or breaks in the mesh, which generally are not supported without special numerical treatments, such as using interface kernels or mortar methods. Beyond having disconnected elements, the overlap means the volume of the mesh does not match the physical space volume, raising concerns about accuracy.

We support two heuristics to detect these overlaps:

• detecting when the centroid of an element is inside another element

• detecting when a node of an element is inside another element

Non-conformality check

Turn this check on with the "examine_non_conformality" parameter.

Non-conformality in MOOSE is generally only supported if it is arising from adaptive mesh refinement created by the underlying mesh library. Additional information about the parent/child relationship between coarse and fine elements is stored at the element level. However, numerous external meshes, especially arising from simulations using adaptive mesh refinement, will present non-conformality. To support them, we usually resort to special numerical treatments, such as mortar methods.

Non-conformality is detected by this diagnostic by looking for nodes that are near an element within a tolerance but not part of this element's nodes.

Elements and sides local Jacobian check

The local Jacobian is checked for positivity for every element and sides. Negative Jacobians are a common issue with a poor, usually externally generated, mesh.

Example input syntax: all diagnostics turned on

In this example, we examine a very basic mesh with all the diagnostics offered by the MeshDiagnosticsGenerator. This simple mesh presents no issue.

[Mesh]
  [base]
    type = GeneratedMeshGenerator
    dim = 2
    nx = 2
    ny = 2
  []
  [diag]
    type = MeshDiagnosticsGenerator
    input = base
    examine_element_overlap = WARNING
    examine_element_types = WARNING
    examine_element_volumes = WARNING
    examine_non_conformality = WARNING
    examine_nonplanar_sides = INFO
    examine_sidesets_orientation = WARNING
    search_for_adaptivity_nonconformality = WARNING
    check_local_jacobian = WARNING
  []
[]

[Outputs]
  exodus = true
[]

Input Parameters