Understanding the Automatic Element Size calculation

To have the software compute an estimated element length based on the selected geometry, use the Automatic Element Size option on the meshing dialog boxes. The software bases this estimate on a number of different criteria and factors.

• With a 2D mesh, the software performs one set of calculations to determine the estimated size.

• With a 3D mesh, the software first performs the 2D calculations and then proceeds with further evaluations to determine the estimated size of the solid elements.

Note:

The element size calculated by Automatic Element Size is an estimate based upon certain characteristics of the currently selected geometry. You should always carefully evaluate your model and use good engineering judgment when determining the element size, regardless of whether you accept the software’s estimate or specify a different size. This evaluation should consider both the unique features of your model's geometry and the requirements of your analysis.

2D calculations

When calculating the automatic element size for a 2D mesh, the software first determines the area of each face as well as the average area of all selected faces. It then evaluates the selected geometry for a number of other factors, such as the total number of edges on those faces, the number of mesh points, and the number of loops. This evaluation also includes an assessment of the type of geometry selected, such as whether a face is flat or non flat, or whether the geometry itself is periodic. The software then generates an initial estimate of the total number of elements required to mesh the selected geometry.

The software uses average area and estimated total number of elements calculations to determine the estimated element length. The estimated length is equal to the square root of the sum of the total face area for all faces divided by the sum of the total number of elements for all faces, or:

Finally, the software validates that the calculated element length is:

• 1.5 * the specified Snap Tolerance (Meshing Preferences dialog box).

3D calculations

When calculating the automatic element size for a 3D mesh, the software begins by performing the 2D calculations on all the faces in the selected volumes to obtain an initial element size. The software then works to determine how to adjust this element size for tetrahedral elements.

With a 3D mesh, the software tries to determine the number of tetrahedral elements necessary to mesh the selected volume. The software calculates the total volume, total area, and total number of faces across all selected volumes. For each selected body, the software then evaluates the ratio of its surface area to its volume. This helps the software understand basic information about the overall shape of a part, such as whether it is chunky or thin-walled. Using these geometry characteristics, the software determines the target number of tetrahedral elements needed to mesh the selected volume.

The software then adjusts the computed number of tetrahedral elements as necessary to ensure that this number falls between appropriate maximum and minimum bounds on the number of elements for the specified geometry. The software uses heuristics to determine the maximum and minimum bounds. Once an appropriate total number of elements has been determined, the software then divides the volume by the total number of elements to calculate the estimated element size.

Finally, the software validates that the calculated element size is:

• 1.5 * the specified Snap Tolerance (Meshing Preferences dialog box).

• <0.5(Volume1/3)

Learn more

Setting element size

Element size for acoustic analysis

Understanding curvature-based size variation

Understanding the Snap Tolerance value

Show Tiny Edges

Multi-block decomposition in meshing

Controlling the proximity of nodes to the CAD Geometry

Understanding the mesh update process

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Understanding the Automatic Element Size calculation, Simcenter 3D 2021.1 Series

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