Understanding the Auto Fix Failed Elements process

The Auto Fix Failed Elements option in the 3D Tetrahedral Mesh dialog box lets you control whether the software tries to automatically repair any detected element quality problems.

Quality criteria evaluated by Auto Fix Failed Elements

Auto Fix Failed Elements uses the following criteria to assess the elements' quality:

• Jacobian, based on the specified Max Jacobian value in the 3D Tetrahedral Mesh dialog box.

• Aspect ratio, based on the specified Aspect Ratio tolerance in the Element Quality Check dialog box.For more information, see Evaluating element quality.

• Tet collapse ratio, based on the specified Tet Collapse tolerance in the Element Quality Check dialog box.Note: The availability of the Tet Collapse tolerance value in the Element Quality Check dialog box depends on the specified solver environment.For more information, see Evaluating element quality.

Repair strategies used by Auto Fix Failed Elements

With Auto Fix Failed Elements, the strategy the software uses to repair element quality issues depends on the quality criteria that the element failed.

• For elements that exceed the specified Max Jacobian value, the software straightens the elements' midnodes to eliminate the issue. The software does not remesh the associated surface or body.

• For elements that exceed the specified Aspect Ratio tolerance, the software remeshes any surfaces associated with those elements. The software never removes elements that exceed the Aspect Ratio.

• For elements that exceed the specified Tet Collapse tolerance, whether the software removes the failing elements or remeshes the associated surfaces depends on the element's topology and the degree to which the element exceeds the tolerance.If the software removes an element, it maintains the connectivity of the nodes on the surrounding elements such that the mesh remains contiguous. The software removes elements that fail Tet Collapse when:The element is completely flat and all its nodes lie on the outer surfaces of the volume. For all other element configurations (for example, when an element is not completely flat or at least one node located in the volume's interior), the software remeshes all surfaces associated with that element.The element's Tet Collapse ratio exceeds 200.The element's Tet Collapse ratio is between 100 and 200 and all four of its corner nodes lie on the outer surfaces of the volume.

Details of the Auto Fixed Failed Elements remeshing process

When the software determines that the surface must be remeshed, Auto Fix Failed Elements:

1. Reduces the element size on the surface by approximately 10% and generates a new surface mesh.

2. Uses the new surface mesh to generate a new mesh on the volume.

3. Reevaluates the element quality in the new mesh.If the elements pass the quality threshold values, the software saves the new mesh.If any elements fail the quality threshold values, the software repeats this process.

The software continues to repeat the remeshing and quality checking process approximately six times. If there are elements that fail the quality checks after six iterations, the software reduces the element size on all surfaces by 10% and then generates new surface and volume meshes.

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Understanding the tetrahedral meshing process

Understanding 3D tetrahedral mesh quality evaluation

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Controlling the size of interior elements in a 3D tetrahedral mesh

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Understanding the Auto Fix Failed Elements process, Simcenter 3D 2021.1 Series

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