Mesh and Geometry

Geometry

The Partition Domains Geometry Operation

A new geometry operation, Partition Domains, enables you to partition selected domains in various ways in 2D and 3D by specifying curves and surfaces, respectively. For example, you can partition the domain of a 3D geometry by the extensions of selected faces of the geometry. This extends a face into the adjacent face of a domain in order to partition that domain.

This function serves multiple purposes when modeling. It can be useful in cases where it would be better to mesh a certain part of the geometry with a structured mesh instead of an unstructured mesh, but the domains are not suitable for mapped or swept meshing. Partitioning can also be an important tool when building tetrahedral meshes by subdividing a complex-shaped (highly nonconvex) domain into domains that are easier to mesh. Furthermore, it can increase the level of (shared-memory) parallelization during meshing.

A Partition Domains node can be placed at any position in a list of subnodes under the Geometry node. This means that the operation can partition output geometries before or after performing Form Union/Assembly, Assembly Geometries, and Virtual Geometries operations.

The workflow of the Partition Domain operation. The workflow of the Partition Domain operation.

The workflow of the Partition Domain operation.

If the original geometry was meshed, it would have been meshed using unstructured tetrahedra, which may not be optimal. By selecting two faces of the geometry, and the Partition with extended faces option, you can create a partitioned geometry that will support the automatic hexahedral meshing of the different domains.

Geometry Entity-Level Control for Output Selections

The new COMSOL Multiphysics release includes improvements to the automatically generated selections from geometry operations. It is now possible to control and select the entity level (point, edge, face, or domain) of selections generated by the geometry sequence to use in other operations, such as when defining physics, materials, or meshing. When building your own geometry parts for use in the Parts Library, you can control which selections are visible to users.

Mesh

More Robust Tetrahedral Meshing

A new algorithm enables the Free Tetrahedral operation to succeed in meshing geometries that previously resulted in errors such as "Failed to respect boundary element edge on geometry face" or "Internal error in boundary respecting". The default meshing method used in COMSOL Multiphysics version 5.2 is a hybrid between the old and new methods. With the Tessellation Method set to Automatic, the old method is used first, and if it fails, the new method is then applied. You can optionally choose to use only the old or new method by setting the Tessellation Method to Delaunay or Delaunay (alternative method), respectively.

The mesh used in the Fit Connection in a Mountain Bike Fork tutorial model. The mesh used in the Fit Connection in a Mountain Bike Fork tutorial model.

The mesh used in the Fit Connection in a Mountain Bike Fork tutorial model.

The new tetrahedral mesher enables automatic meshing without modifying the mesh settings for a much larger class of CAD geometries than in previous versions of the software.

Import External Mesh Parts

The process of importing an externally defined mesh (e.g., a surface mesh defined by an STL file) as a geometry is now easier and more robust. Simply add an Import subnode under the Geometry node, browse to the mesh file to import, and click on the Import button. COMSOL Multiphysics automatically adds a Mesh Part node (under the Global Definitions node) that imports the mesh file and creates a geometry from the imported mesh. The Form solids from surface objects check box controls whether or not the geometry import operation converts an imported closed surface mesh to a solid object.

When using a mesh part, you have access to the same set of mesh partitioning operations, such as Ball, Box, and Logical Expression, as an imported mesh under the Mesh node. If you use any of these operations to modify the imported mesh part, the corresponding geometry import operation automatically detects that a rebuild is needed. When you rebuild the geometry import operation, all selections in the corresponding component are automatically updated to the new geometry.

If you import a geometry from a mesh part that refers to a NASTRANĀ® file containing material information, nodes defining the materials automatically appear under the Materials node in the component of the geometry. The geometry import operation also transfers selections defined by the NASTRANĀ® file.


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