Swept

The node (

) creates a swept mesh on a domain in 3D by sweeping the mesh from the source faces along the domain to the opposite destination faces, as shown in Figure 8-58. A swept mesh is an example of a semistructured mesh since it is structured in the sweep direction and can be either structured or unstructured orthogonally to the direction of the sweep. A swept mesh is typically a hexahedral mesh (hex mesh) or a prism mesh.

Figure 8-58: Generation of a hexahedral mesh. A mapped mesh is built on the source face, highlighted in blue. This mesh is swept along the circular linking edges (highlighted in red), resulting in a hexahedral mesh, as shown to the right.

You can control the number, size, and distribution of elements using the Size and Distribution subnodes. The node only reads properties from nodes defined on the entire geometry or on the domain level and nodes defined on the domain level.

Classifications

Each face about a domain that is to be operated on by the swept mesher is classified as either a source face, a destination face, or a linking face. The linking faces are the faces connecting the source and destination faces (see Figure 8-59).

The linking edges are the edges, or the chains of edges, connecting the source and destination faces.

Figure 8-59: Classification of the boundaries and edges about a domain used for swept meshing. Two faces in the foreground are hidden for visibility.

Requirements

For the sweeping technique to work, the geometry must satisfy these criteria:

•

Each domain must be bounded by one shell; that is, a domain must not contain holes except if they penetrate both source and destination.

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The source and destination for a domain must be opposite each another in the domain’s topology.

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Each destination face must correspond to one or more source faces (see Figure 8-60).

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Each source face must correspond to precisely one destination face or a subset of it (see Figure 8-60). If needed, use a Cross Section operation to make an imprint of the source faces on the destination.

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Coincident source and destination faces are allowed, as when sweeping the mesh a full revolution around an axis.

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The cross section along the direction of the sweep for a domain must be topologically constant.

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There must be at least one linking edge or chain of edges connecting the source and destination faces.

Figure 8-60: Determination of sweep direction. If the number of faces differ on source and destination, the source will always have the larger number of faces.

Even if the original geometry does not fulfill the above criteria, it is sometimes possible to partition the geometry in order to obtain domains where a swept mesh can be created.

If any of the faces about a domain is meshed prior to the sweeping operation, the following must be fulfilled:

•

If the source and destination faces are meshed, these meshes must match.

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If any of the linking faces are meshed, these must be meshed with structured quad meshes generated by the Mapped mesher.

The swept mesher can handle domains with multiple linking faces in the sweep direction, as seen in Figure 8-60.

To create a swept mesh:

•

Right-click in the Graphics window and select (

) from The Graphics Context Menu. A preselection of unmeshed domains will be added to the . A preselection of boundaries will be added in the list of and adjacent domains will be added to the .

•

In the toolbar, click the (

) button. A preselection of unmeshed domains will be added to the . A preselection of boundaries will be added in the list of and the adjacent domains will be added to the .

•

Right-click a 3D node and select .

Domain Selection

Specify the domains where you want a swept mesh. Choose the level of the geometry from the list:

•

Choose to generate a swept mesh for the remaining, unmeshed domains.

•

Choose to specify swept mesh for the entire geometry.

•

Choose to specify the domains for which you want a swept mesh. Choose in the list to select the domains in the window or choose to select all domains.

Source Faces

Click the button to toggle between turning ON

and OFF

selections.

In most cases the swept mesher can automatically identify source and destination faces from the geometry. To specify the source faces directly, activate the list and select the faces defining the source of the sweep operation in the window.

Click the button (

) to swap the faces in the source list above and the faces in the destination list in the section below.

Destination Faces

To specify the destination faces directly, activate the list and select the faces defining the destination of the sweep operation in the window.

Sweep Method

Face Meshing Method

In the list, you can specify how unmeshed source faces are automatically meshed by the Swept operation:

•

Select to generate a surface mesh with quadrilateral elements. This is the default meshing method.

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Select to generate a surface mesh with triangular elements.

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Select any of the legacy versions to generate a surface mesh with quadrilateral elements using an algorithm used in earlier versions of the software.

Sweeping Path

Use the list if you want to specify the shape of the sweep path:

•

The default, , means that the sweeping algorithm automatically tries to determine if the sweep path is straight or circular; otherwise, a general approach is used.

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means that all interior mesh points are located on straight lines between the corresponding source and destination points.

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means that all interior mesh points are located on circular arcs between the corresponding source and destination points, as shown in Figure 8-58.

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means that the positions of the interior mesh points are determined by a general interpolation procedure, as shown in Figure 8-61.

Figure 8-61: An hourglass-shaped geometry in which an unstructured quad mesh is swept using a general interpolation procedure.

Destination Mesh

Use the list if you want to specify the method to be used for transferring the source mesh to the destination:

•

The default, , means that the algorithm automatically tries to determine a suitable method for creating the destination mesh.

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where source and destinations have the same shape, up to a scaling factor.

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when the source and destination have different shape. For example, when going from a circular to a rectangular cross-section, or going from a planar source face to a curved destination face.

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means that the destination mesh is created from the source mesh by a projection technique. This is useful when the source and destination faces are close to each other and have different shape.

Control Entities

Select the check box to smooth the transition in element size across removed control entities. When selected, the mesher adjusts the sizes of the mesh elements to get a smoother transition from large to small elements by adjusting the locations of the mesh vertices on the entity that is removed. Clear the check box to not adjust the mesh. You can specify the number of smoothing iterations in the field. In the field you can specify the maximum element depth for the mesh points to be smoothed.

Figure 8-62: Comparing meshes where Smooth across removed control entities has been used vs. not used.

Linking Faces

You can choose between two different interpolation methods for the linking faces in the list. This specifies how the mapped mesher, which is used by the swept mesher for the linking faces, determines the positions of the interior mesh points. For more information on the different options see Mapped.