FEM MeshNetgenFromShape

Description

For a finite element analysis, the geometry needs to be discretized into a FEM Mesh. This command uses Netgen (which needs to be installed on the system) to generate the mesh. Netgen meshes are not supported by Elmer.

Depending on your operating system and installation package, Netgen might be bundled with FreeCAD or not. For further information see FEM Install.

introduced in 1.0: The refactored Netgen mesher is available. It can be activated in the preferences and is installed via Python bindings as explained on the aforementioned FEM Install page.

Usage

1. Select the shape you want to analyze. For a volume, this needs to be solid or compsolid. A compsolid is necessary if your part is made from multiple materials (a compsolid can be created with the Part BooleanFragments command).
2. There are several ways to invoke the command:
   • Press the Mesh From Shape by Netgen button.
   • Select the Mesh → Mesh From Shape by Netgen option from the menu.
3. Optionally, set the max/min element size (the default setting usually creates meshes that are too coarse) and element order (using the Second Order checkbox).
4. Optionally, change the Fineness to one of the predefined choices or choose UserDefined and manually edit the parameters.
5. Click the Apply button to generate the mesh. introduced in 1.0: Optionally, use the Cancel button to abort meshing if using the new Netgen implementation.
6. Click the OK button to generate the mesh and close the dialogue. You can also click the Cancel button to cancel the changes or creation of the mesh object.

Properties - Legacy Netgen

• DataMax. Size: Maximum size of the element in mm.
• DataMin. Size: introduced in 1.0: Minimum size of the element in mm.
• DataSecond order: Second order elements contain more nodes per element. Usually, it is enough to use rougher mesh to obtain same solution precision as with the first order elements,
  • true (default); second order elements,
  • false; first order elements.
• DataFineness: Offers predefined levels of mesh density.
• DataGrowth Rate: Defines how much adjacent elements can differ in size.
• DataNb. Segs per Edge: Defines the minimum number of mesh segments per edge.
• DataNb. Segs per Radius: Defines the minimum number of mesh segments per radius.
• DataOptimize:
  • true (default): applies optimization algorithm to improve mesh quality
  • false

Properties - Refactored Netgen

• DataBad Element Limit: Limit for max element angle (150-180).
• DataBase Element Np: If non-zero, baseelement must have BaseElementlNp points.
• DataBlock Fill: If enabled, block filling is performed.
• DataCheck Chart Boundary: If enabled, chart boundary is checked.
• DataCheck Impossible
• DataCheck Overlap: If enabled, overlapping surfaces are checked.
• DataCheck Overlapping Boundary: If enabled, overlapping surface mesh is checked before volume meshing.
• DataClose Edge Factor: Factor to restrict meshing based on close edges.
• DataCurvature Safety: Safety factor for curvatures (elements per radius).
• DataDelaunay: If enabled, Delaunay algorithm is used for 3D meshing.
• DataDelaunay2d: If enabled, Delaunay algorithm is used for 2D meshing.
• DataElement Order: High order element curvature.
• DataElement Size Weight: Weight of element size with respect to element shape.
• DataEnd Step: Last step:
  • AnalyzeGeometry
  • MeshEdges
  • MeshSurface
  • OptimizeSurface
  • MeshVolume
  • OptimizeVolume
• DataFill Distance: Block filling up to distance.
• DataFineness: Offers predefined levels of mesh density:
  • VeryCoarse
  • Coarse
  • Moderate
  • Fine
  • VeryFine
  • UserDefined
• DataGive Up Tolerance: Give up quality class for 3D meshing.
• DataGive Up Tolerance2d: Give up quality class for 2D meshing.
• DataGive Up Tolerance Open Quads: Give up quality class for closing open quads, greater than 100 for free pyramids.
• DataGlue: introduced in 1.1: Glue shapes to get a conformal mesh.
• DataGrowth Rate: Grading for local h.
• DataHeal Shape: If enabled, shape is healed before meshing.
• DataInvert Tets
• DataInvert Trigs
• DataLocal H: If enabled, uses local h.
• DataMax Outer Steps: Maximum outer steps.
• DataMax Size: Maximum size of the element in mm.
• DataMin Size: Minimum size of the element in mm.
• DataOnly3d Domain Nr
• DataOptimization Error Power: Power of error to approximate max error optimization.
• DataOptimization Steps2d: Number of 2D optimization steps.
• DataOptimization Steps3d: Number of 3D optimization steps.
• DataOptimize2d: 2D optimization strategy.
• DataOptimize3d: 3D optimization strategy.
• DataParallel Meshing: If enabled, uses parallel meshing.
• DataQuad Dominated: If enabled, uses quad dominated surface meshing.
• DataRelinner Safety: Radius of active environment (times h).
• DataSafety: Radius of local environment (times h).
• DataSecond Order: If enabled, uses second order element meshing.
• DataSecond Order Linear: If enabled, second order nodes are created by linear interpolation.
• DataSegments Per Edge: Minimum number of segments per edge.
• DataSloppy: Quality tolerances are handled less careful.
• DataStar Shape Class: Class starting star-shape filling.
• DataStart In Surface: If enabled, starts surface meshing from everywhere in surface.
• DataStart Step: First step:
  • AnalyzeGeometry
  • MeshEdges
  • MeshSurface
  • OptimizeSurface
  • MeshVolume
  • OptimizeVolume
• DataTry Hexes: If enabled, tries hexahedral elements.
• DataUse Local H: If enabled, uses local H.
• DataZRefine: introduced in 1.1: Z-refinement for extruded shapes, can create extruded hex meshes when combined with the Quad Dominated property. Will work only for first-order meshes (unless the generated elements are all hexahedrons):
  • No - Z-refinement is disabled
  • Regular - all elements have the same height
  • Custom - the height of each element must be specified
• DataZRefine Direction: introduced in 1.1: Z-refinement direction (change if the shape is extruded in a direction other than the Z axis).
• DataZRefine Size: introduced in 1.1: Z-refinement size (element height) given as a fraction of the shape size (total height). For a regular partition, only one value is needed.