Mesh Parts
You can use mesh parts for importing and preparing a mesh for use in a geometry sequence or meshing sequence. A mesh part is defined by an imported mesh from an STL, VRML, NASTRAN, MPHBIN, or MPHTXT file, mesh data imported from results, or from some other meshing sequence. In addition, you can use mesh import operations to delete or partition parts of the mesh, for example, to prepare the imported mesh for use in a geometry sequence or meshing sequence, where you refer to the mesh part in an Import node. To insert the mesh into the new component, you can use a Copy node in the meshing sequence, where you use the mesh from the mesh part as the source.
When importing a NASTRAN file in the mesh part, it might include material definition, variables, and selections. All those properties are transferred to the component where you import the mesh part.
You can add mesh parts from the Global Definitions node () by right-clicking it and, from the Mesh Parts submenu, select 3D Part, 2D Part, or 1D Part. If a Mesh Parts node () already exists under Global Definitions, you can add another mesh part by right-clicking it and then select 3D Part, 2D Part, or 1D Part.
Under a Mesh Part node you add nodes for importing and modifying an externally generated mesh. An Import node (see Importing Meshes) is automatically added to import a mesh. In 2D and 3D, you can then add additional nodes for partitioning the mesh, deleting and joining entities, creating entities, and Remeshing Imported Meshes. Such operations can be useful to define additional domains, for example. There is also a View node with view settings (see User-Defined Views) below the mesh feature nodes.
In a geometry sequence or part you can create an instance of the mesh part by right-clicking the Geometry node and adding an Import node (see Import in the Geometry Modeling and CAD Tools chapter). Then choose Mesh or STL (in 3D) or Mesh (in 1D and 2D) from the Source list and choose the mesh part from Mesh list below to use the mesh part in the geometry sequence.
The Settings window for a Mesh Part node contains the following sections:
Mesh Settings
Select the Build new operations automatically check box to allow new operations for this mesh part to build automatically. Clear the check box to require that the Build Selected or Build All buttons are clicked in order for the operations to build. The default value is controlled by the preference setting Mesh>Build new operations automatically. Select In new meshes check box to always build operations directly, unless overridden by the settings for an individual mesh part.
Units
For mesh files that are unitless, the physical size of an imported mesh is independent of the length unit of the mesh part. For mesh files that define a unit, the imported mesh is scaled to match the unit of the mesh part, if the Use units check box is selected. You can also select this check box to use the length unit and angular unit (which you specify using the Length unit list and Angular unit list, respectively) in the nodes appearing under the Mesh Part node and to specify the length unit of the resulting file when exporting the mesh to a file format that supports length units.
If the mesh part and the component referring to the mesh part have different unit systems, the resulting geometry is scaled.
STL Import 1 — Generating a Geometry from an Imported Mesh: Application Library path COMSOL_Multiphysics/Meshing_Tutorials/stl_vertebra_import