Free Quad

) to create an unstructured quadrilateral mesh on boundaries in 3D and domains in 2D, also for imported meshes in 3D. You can control the number, size, distribution, and refinement of elements by using Size, Size Expression, Size, and Corner Refinement subnodes (only and subnodes are available for imported meshes). A remeshing operation in an imported meshing sequence separates the selected boundaries from the mesh, creates geometry from the separated mesh, meshes the geometry, and then copies the new generated mesh onto the original imported mesh. This operation has the following practical implications:

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External edges of the selection are kept unchanged, while internal edges are remeshed.

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Before generating geometry, the mesh is simplified according to the settings in the section (see below).

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If remeshing fails, the error message might be referring to a problem in generating geometry from the mesh.


	Only boundaries with first-order elements can be remeshed.

To create an unstructured quadrilateral mesh:

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In the ribbon toolbar (Windows), from the (

) menu choose .

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From the contextual toolbar (macOS and Linux), choose from the menu (

) (3D components) or click (2D components).

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Right-click a node and choose . For 3D components, this is selected from the menu except when used for imported meshes.


	The quadrilateral mesh generator does not strictly create only quadrilateral elements. In places of the geometry where it judges it as necessary, it can also create triangular elements.

Then enter the properties for the quadrilateral meshing operation using the following sections:

Boundaries (3D) / Domains (2D)

Define the boundaries (3D) or domains (2D) where you want to create an unstructured quad mesh. Choose the level of the geometry from the list:

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Choose to specify unstructured quad mesh for remaining, unmeshed domains.

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Choose to create an unstructured quad mesh in the entire geometry.

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Choose (3D) or (2D) to specify the geometric entities for which you want to create an unstructured quad mesh. Choose in the list to select the boundaries or domains in the window or choose (3D) or (2D) to select all boundaries or all domains.

For imported meshes in 3D, the available options in the list are and .

Scale Geometry

To scale the geometry during the meshing operation, change the x-scale, y-scale, and z-scale in 3D to positive real numbers. If any of the scale factors are not equal to one, the software scales the geometry in the x, y, and z directions before meshing; after meshing, it restores the geometry and mesh to fit the original size. The scale factors make it possible to generate meshes that are anisotropic. They are also useful if the mesh generator creates many elements due to a thin geometry or if the mesh generation fails due to large aspect ratios in the geometry.

Control Entities

This section is not available for imported meshes.

Select the check box to smooth the transition in element size across removed control entities. You can specify the number of smoothing iterations in the field. In the field you can specify the maximum element depth, from the boundary layer interface, for the mesh points to be smoothed.

Tessellation

From the list, choose the tessellation method to use for creating an unstructured quadrilateral mesh:

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Select (the default) to make the mesh generator determine the best algorithm to use for each domain.

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Select to use the algorithm available in version 5.2 and earlier versions of COMSOL Multiphysics.

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Select to use the algorithm available in version 5.2a of COMSOL Multiphysics, which, in addition to earlier versions of the free quad algorithm, has support for templates.

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Select to use the algorithm available in version 5.4 of COMSOL Multiphysics.

Mesh Preprocessing

This section is only available for imported meshes.

You can optionally simplify the mesh. The simplification can remove small defects typically present in mesh data from measurements, such as tomography, and it can speed up the process by removing unnecessary elements from all kind of meshes. The check box is selected by default to enable simplification.

The (default value: 0.01) is relative to the dimensions of the entire geometry and specifies a global limit for how much the mesh can be modified. The (default value: 1) is relative to the local feature size, as estimated by the algorithm, and is combined with the global limit to produce a limit for how much the mesh can be modified at a certain location. If the mesh contains many defects that you want to remove, you could try to increase the value of the . If the mesh describes the desired geometry with high accuracy, you may want to decrease this factor instead.