2D mapped meshing

Use the 2D Mapped Mesh command to generate a structured mesh of linear or parabolic triangular or quadrilateral elements on selected faces. Mapped meshes allow you to better control the distribution of elements across a surface than free meshes. Mapped meshes are useful, for example, for meshing certain types of geometry, such as fillets and cylinders, where regular meshes are desirable. The following graphic shows an example of a mapped mesh on a three-sided (A) and four-sided (B) face.

Note:

If you generate a mapped mesh on a three-sided face, you can control the vertex at which the mesh degenerates.

Supported topology for mapped meshing

To be a candidate for mapped meshing, a face must be comprised of a single loop (boundary). You cannot define a mapped mesh on a surface that contains an interior loop or hole. Additionally, the number of topological sides on a face affects whether you need to select the Attempt Multi-Block Decomposition option in the Mesh Options group to generate a structured mesh.

• If a face has three or four sides, you can generate a structured mesh either without or with the Attempt Multi-Block Decomposition option selected.

• If a face has five or more sides, you must select the Attempt Mult-Block Decomposition option.

A topological side can be a composite of several edges or curves. If a selected face has more than three or four edges, the software tries to select logical corners to create composite sides. After you click Preview to examine the initial mesh, you can use the Define Corners options to refine the endpoints for each composite side, if necessary. The following graphic shows an example of a surface comprised of a number of edges. To define a mapped mesh on this surface, you can select the corners shown in red to define the composite sides.

You can also use 2D Mapped Mesh to generate mapped meshes on certain non-planar faces that are comprised of multiple loops, such as a cylindrical or spherical surface. With a cylindrical or spherical surface, the software internally tries to divide the surface into three or four sided regions that can be mapped meshed. If the software is unable to divide the surface appropriately, it does not generate a mesh on that surface.

Mapped meshing process

With 2D Mapped Mesh, after you select an appropriate face, the software automatically calculates the locations of the corners. Using the element size you specify, it also creates Number on Edge type edge densities to control the distribution of elements along the edges of the selected face. Note that:

• Three sided surfaces must have an equal number of elements on the two edges adjacent to the corner where the mesh degenerates.

• Four sided surfaces can have a different number of elements on each side.

The Preview Mapped Mesh option lets you preview the mesh. As a best practice, you should always preview the mesh before you pick OK or Apply. You can make adjustments to the previewed mapped mesh before the software actually generates it. For example, with the previewed mesh displayed, you can redefine the corners of the faces or modify the edge density element count along selected edges. You can also modify the element size.

Controlling mapped meshes on three-sided surfaces

For mapped meshes three-sided surfaces, you can control whether the software uses triangular elements in the mesh.

• You can have the mapped mesh of quadrilateral elements degenerate into a mesh of triangular elements in a designated corner. Use the Define Corners option in the 2D Mapped Mesh dialog box to control the corner at which the mesh degenerates. The Define Corners option requires that you select four corners. However, if you are working with a three sided surface, simply select one corner twice. The last corner you select is the corner where the mesh degenerates.

• You can select the Quad Only on 3 Sided Faces option in the Mesh Options group to create a mesh that does not contain any triangular elements. With this option, if the software is unable to maintain parity (an even number of nodes along the boundary of a face) due to constraints from existing meshes on surrounding faces, it creates a mapped mesh that contains a singular triangular element. The following example shows a mapped mesh on a three-sided face created with the Quad Only on 3 Sided Faces option selected.

Locations of mesh points respected

If you create a mapped mesh on a face that contains a mesh point, the software respects the location of that mesh point and optimizes the mapping so that the mesh remains as structured as possible in that region.

Using multi-block decomposition to create structured meshes on more complex geometry

You can use the Attempt Multi-Block Decomposition option in the Mesh Options group to create a structured mesh on:

• Faces that are comprised of a single loop (boundary) but that have five or more sides.

• Faces where the software cannot successfully generate a mapped mesh.

With this option, the software internally subdivides faces with a number of near 90° corners into a cluster of convex regions. The software then generates meshes on each convex region. In general, the resulting meshes are more structured in nature.

For more information, see Multi-block decomposition in meshing.

Retaining free meshes if the mapped mesh fails

If the software is unable to generate a mapped mesh on one or more of the faces you select, you can use the Store Free Mesh if Mapped Mesh Fails option in Customer Defaults to control whether the software generates a free mesh on those faces instead. For example, you may want to clear the Store Free Mesh if Mapped Mesh Fails check box in situations where you want to more clearly see any faces on which the software failed to generate a mapped mesh.

To access this option:

1. Choose File→Utilities→Customer Defaults.

2. In the Customer Defaults dialog box, select Simulation→Pre/Post→Meshing.

3. On the Meshing page, either select or clear the Store Free Mesh if Mapped Mesh Fails check box.

Where do I find it?

Application	Pre/Post
Prerequisite	A FEM file is the work part and displayed part
Command Finder	2D Mapped Mesh

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2D mapped meshing, Simcenter 3D 2021.1 Series

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