Import

Import mesh from a file or from another meshing sequence. You can import a mesh from a COMSOL Multiphysics native file. In 3D you can also import meshes from NASTRAN, STL, or VRML files. In 2D you can also import 2D meshes from NASTRAN (the third coordinate must then be the same for all mesh points).

Syntax

model.mesh(<tag>).create(<ftag>,"Import");

model.mesh(<tag>).feature(<ftag>).set(property,<value>);

model.mesh(<tag>).feature(<ftag>).getType(property);

model.mesh(<tag>).feature(<ftag>).importData();

Description

Use model.mesh(<tag>).create(<ftag>,"Import") to import a mesh into a sequence without a corresponding geometry. It is only possible to use this feature when the geometry sequence is empty. If the sequence already contains a mesh, the imported mesh is added to the existing mesh.

Use model.mesh(<tag>).feature(<ftag>).importData() to import the file again.

The following mesh formats are supported:


format	file extension
COMSOL Multiphysics text file	.mphtxt
COMSOL Multiphysics binary file	.mphbin
NASTRAN file	.nas \| .bdf \| .dat

The following properties are available:

Table 4-40: Available Properties for the Mesh Import
Property	Values	Default	Description
allowshellpartition	on \| off	on	Specifies whether the boundary entities that are defined based on the data in the file can be split into smaller parts.
data	all \| mesh	all	Specifies the data to import from the NASTRAN file.
elemsplit	on \| off	off	Specifies if mesh elements of different element forms get different domain labels when importing a NASTRAN file.
facepartition	auto \| minimal \| detectfaces \| manual	auto	Boundary partitioning algorithm. detectfaces is only available in 3D, and manual is only available in 2D.
filename	String		The filename.
linearelem	on \| off	off	Specifies if the elements in the NASTRAN file are imported as linear elements.
materialsplit	on \| off	on	Specifies if material data in the NASTRAN file is used to determine the domain partitioning of the domain elements.
selcreation	on \| off	on	Specifies whether selections corresponding to the groups of domain and boundary elements in the NASTRAN file should be created.
sequence	String		Meshing sequence name.
source	file \| sequence \| native \| nastran \| stlvrml	file	Source for the import.

The properties elemsplit, linearelem, materialsplit, and data are only used for import of NASTRAN files. The properties selcreation and allowshellpartition are only used when materialsplit is on.

elemsplit specifies if mesh elements of different element forms — that is, tetrahedral, pyramid, prism, or hexahedral — get different domain labels. The default value is off.

linearelem specifies if the elements in the NASTRAN file are imported as linear elements. If the value is on all imported elements are linear. Otherwise, the order of the imported elements is determined from the order of the elements in the file. The default value is off.

materialsplit determines if material data in the file is used (if available) to determine the domain partitioning of the domain elements. If the value is off all domain elements in the imported mesh belongs to the same domain if possible. The default value is off.

If you set facepartition to minimal, the operation keeps the original partition from the file (if any), adding minimal partitioning in order to satisfy topological requirements.

If you set facepartition to manual, you can use the following properties. If you set any of these properties without setting facepartition to manual, the operation automatically switches facepartition to manual.

Table 4-41: Valid Property/Value Pairs for facepartition = manual
Property	Value	Default	Description
curvedface	auto \| manual	auto	Control parameters for partitioning of curved faces. Available only in 3D.
faceangle	double	360 degrees	Maximum angle between any two boundary elements in the same face.
minareaplane	double	0.005	Minimum relative area of face to be considered planar.
neighangle	double	40 degrees	Maximum angle between a boundary element and a neighbor that causes the elements to be part of the same boundary domain if possible.
planar	on \| off	on	Detect planar faces.
planarangle	double	0.6 degrees	Maximum angle between boundary element normal and a neighbor that causes the element to be a part the planar face if possible.

The following properties are available in 3D when facepartition is set to detectfaces:

Table 4-42: Valid Property/Value Pairs for facepartition = detectfaces
Property	Value	Default	Description
detectadjfillets	on \| off	on	Whether to detect cylindrical faces adjacent to the detected planar faces.
detectfacesplanar	on \| off	on	Whether to detect planar faces.
facemaxangle	double	40 degrees	Maximum tolerated angle between neighboring boundary elements in the same face.
planarfacemaxangle	double	0.6 degrees	Maximum tolerated angle between neighboring boundary elements in the same planar face.
planarfaceminareafraction	double	0.005	Minimum relative area for a planar face to be created.

The table below specifies the supported NASTRAN bulk data entries.


bulk data entry
CBAR	CORD2C	CQUAD4	GRID
CHEXA	CORD2R	CQUAD8	MAT1
CORD1C	CORD2S	CTETRA	MAT10
CORD1R	CPENTA	CTRIA3	PSHELL
CORD1S	CPYRAM	CTRIA6	PSOLID

The NASTRAN bulk data format uses reduced second-order elements; that is, the center node on quadrilateral mesh faces (quadNode) and the center node of hexahedral elements (hexNode) are missing. Importing a NASTRAN mesh with second-order elements, COMSOL Multiphysics interpolates the coordinates of these missing node points from the surrounding node points using the following formulas: quadNode = 0.5*quadEdgeNodes - 0.25*quadCornerNodes, where quadEdgeNodes is the sum of the coordinates of the surrounding 4 edge nodes and quadCornerNodes is the sum of the coordinates of the surrounding 4 corner nodes, and hexNode = 0.25*hexEdgeNodes-0.25*hexCornerNodes, where hexEdgeNodes is the sum of the coordinates of the surrounding 12 edge nodes and hexCornerNodes is the sum of the coordinates of the surrounding 8 corner nodes.


	The Import feature does not handle NASTRAN files in free field format where the data fields are separated by blanks.

Compatibility

For 3D mesh sequences, the setting manual of the property facepartition in the mesh Import feature, as well as all the properties associated with this setting, are deprecated as of COMSOL 5.1 and may be removed in a future version. In COMSOL 5.1, these properties are still available with unchanged behavior for backward compatibility.

The following properties from the corresponding COMSOL 3.5a command, meshimport, have been removed:

Table 4-43: Removed Properties
Property	Reason
mcase	Defined by meshing sequence
out	Output mesh provided by meshing sequence