Controlling the proximity of nodes to the CAD Geometry

Pre/Post generates a mesh on the polygon geometry in your FEM file. In some cases, the polygon geometry may diverge slightly from the original CAD geometry. Prior to meshing, the software performs a number of automatic cleanup operations on the polygon geometry. These cleanup operations, for example, remove sliver surfaces and create seams in periodic faces. The software then generates the mesh. However, as a result of these cleanup operations, the nodes may not always be located exactly on the CAD surfaces or edges. While small differences in node position are inconsequential for most types of analysis, they can be significant for the accurate detection of contact.

There are two ways you can control the position of nodes relative to the CAD geometry.

• Prior to 2D or 3D meshing, you can use the Project Nodes to CAD Geometry option (Meshing Preferences dialog box) to project nodes onto the CAD geometry rather than the polygon geometry.

• After meshing, you can use the Adjust Node Proximity to CAD Geometry command to evaluate the proximity of to the original CAD geometry and adjust that proximity, if necessary.

Projecting nodes directly onto the CAD geometry during meshing

Before you create a mesh, you can use the Project Nodes to CAD Geometry option to have the software always project nodes onto the underlying CAD geometry instead of the polygon geometry.

• To turn this capability on in your current session, use the Project Nodes to CAD Geometry option in the Meshing Preferences dialog box.

• To turn this capability on by default, use the Project Nodes to CAD Geometry customer default (located on the Simulation→Meshing→General tab).

Note:

With this option, you must have the idealized part loaded before you can generate a mesh.

Evaluating the proximity of nodes to the CAD geometry on an existing mesh

Use the Adjust Node Proximity to CAD Geometry command to evaluate the proximity of the nodes in a mesh to the original CAD geometry. This lets you evaluate the fidelity of the mesh (which the software creates on the polygon geometry) to the underlying CAD part.

Note:

You must have the idealized part loaded to use the Adjust Node Proximity to CAD Geometry command.

The Adjust Node Proximity to CAD Geometry command is most useful before you perform a contact analysis when you need to ensure the precision of node locations in regions of contact.

Understanding the node proximity evaluation

In the Adjust Node Proximity to CAD Geometry dialog box, you can specify the proximity Tolerance the software uses to evaluate a node's proximity to the underlying CAD edge or face.

• If a node's distance from the underlying CAD geometry is within this value, it passes the proximity check.

• If a node's distance from the underlying CAD geometry exceeds this value, it fails the proximity check.

If your mesh includes parabolic elements, you can use the Include Midnodes option to control whether the software includes the midnodes in the proximity check.

Adjusting node proximity

If you click the Adjust Nodes button in the Adjust Node Proximity to CAD Geometry dialog box, the software moves any failing nodes so that they lie within the specified proximity Tolerance.

For parabolic elements, the software checks their Jacobian value after it has adjusted the proximity of any failing nodes. If you selected the Mixed option from the Midnode Method list (in the 2D Mesh or 3D Tetrahedral Mesh dialog box) when you created the mesh, the software straightens the midnodes of any elements that fail the Jacobian check.

Where do I find it?

Application	Pre/Post
Prerequisite	A FEM file active with the idealized part file loaded
Command Finder	Adjust Node Proximity to CAD Geometry
Menu	Analysis→Finite Element Model Check→Adjust Node Proximity to CAD Geometry

Learn more

Setting element size

Element size for acoustic analysis

Understanding the Automatic Element Size calculation

Understanding curvature-based size variation

Understanding the Snap Tolerance value

Show Tiny Edges

Multi-block decomposition in meshing

Understanding the mesh update process

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Controlling the proximity of nodes to the CAD Geometry, Simcenter 3D 2021.1 Series

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