Midnode placement for parabolic elements

You can use the Midnode Method option in the 2D Mesh and 3D Tetrahedral Mesh dialog boxes to control how the software projects the midnodes or midside nodes of parabolic elements onto the geometry. With the Mixed option, the software projects an element's midnodes to the geometry unless the projection causes the element's Jacobian value to exceed specified the Jacobian threshold.

Moving midnodes to reduce the Jacobian value

If an element's Jacobian value is higher than the specified Jacobian value, the software iteratively moves the midnodes off the geometry to try to improve the Jacobian value. The software incrementally straightens the edge by moving the midnode along a line between the original location and a final straight location. The software first moves the node 25% of the distance along that line, then 50%, then 75%, then 100%.

If the element passes the Jacobian criteria with the node at the 25, 50, or 75% location, then it does adjust the midnode's location further. As a result of this process, the nodes remain closer to the underlying geometry and the quality criteria is satisfied

Controlling the amount of midnode movement

For 2D parabolic triangular meshes and 3D parabolic tetrahedral meshes, you can use the Geometry Tolerance option to control how far the software can move a midnode off the polygon geometry to improve the Jacobian value in 2D triangular free meshes and 3D tetrahedral meshes. This tolerance value controls the maximum amount of linear deviation between the midnode and the geometry.

If you select Mixed from the Midnode Method list, the software projects the midnode to the geometry unless the projection causes the element's Jacobian value to exceed the specified threshold value. You can then use the Geometry Tolerance option to specify the maximum allowed amount of linear deviation between the midnode and the geometry. If the software is unable to position the midnode so that it is within both the specified Jacobian and Geometry Tolerance thresholds, the software remeshes the face or faces associated with the midnode at a smaller element size.

For 2D meshes, if a mesh contains one or more midnodes that exceed the specified Geometry Tolerance value, the software remeshes the associated edges or surfaces. If the surface mesh has an associated tetrahedral mesh, the software first deletes the 3D mesh. It then remeshes the 2D mesh in the appropriate regions and regenerates the solid mesh.

Note:

This remeshing process can negatively impact performance for both 2D and 3D tetrahedral meshes.

Remeshing to modify midnode locations

If the software is unable to position the midnode such that it is within both the specified Jacobian and Geometry Tolerance thresholds, the software remeshes the face or faces associated with the midnode at a smaller element size.

If a mesh contains one or more midnodes that exceed the specified Geometry Tolerance value, the software remeshes the associated edges or surfaces. If the surface mesh has an associated tetrahedral mesh, the software first deletes the 3D mesh. It then remeshes the 2D mesh in the appropriate regions and regenerates the solid mesh.

Note:

This remeshing process can negatively impact performance for both 2D and 3D tetrahedral meshes.

Where do I find it?

Application	Pre/PostDesign Simulation
Prerequisite	A FEM file as the work part and displayed part
Command Finder	2D Mesh 3D Tetrahedral Mesh
Location in dialog box	Mesh Quality Options group

How do I

Create a 3D tetrahedral mesh

Learn more

3D tetrahedral meshing

Understanding the tetrahedral meshing process

Understanding 3D tetrahedral mesh quality evaluation

Creating at least two elements through the thickness of tetrahedral meshes

Understanding the Auto Fix Failed Elements process

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

Quick links

Command reference

Pre/Post video examples

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Midnode placement for parabolic elements, Simcenter 3D 2021.1 Series

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