Tetrameshing

HyperMesh provides several methods of generating a tetrahedral mesh. The standard method creates tetras from an enclosed volume of shell elements, plus several parameters. This provides the user with a lot of control over the final tetra mesh. The volume tetra mesher quickly and automatically creates a tetrahedral mesh on an enclosed volume of surfaces or solid geometry with only a few inputs. Finally, the quick tetra mesher creates a tetra mesh that maintains user specified quality requirements, but may sacrifice details in the shape of the part to do so. All methods are valid in certain situations. The exercise in this section focuses on the standard and volume tetra meshing methods.

In this section, you will learn about:

Expand the sections below to learn more about Volume and Standard Tetrameshing in HyperMesh.

Volume Tetra Meshing

The volume tetra meshing utility, found in the Mesh > Create > Tetra Mesh  pull-down menu and in the Volume tetra subpanel, provides a quick method for generating a tetra mesh.  No initial 2D mesh is required and the tetra mesh can be generated on solid geometry or inside surfaces fully bounding a volume.

Two options are available to control the mesh:

  • Use Proximity – Creates smaller elements next to small features to make a smooth transition from small to large elements.
  • Use Curvature – Will place more elements along curved surfaces based on user specified settings.

          

Standard Tetra Meshing

Standard Tet Meshing involves wrapping a volume in 2D elements and then using that predefined mesh to “grow” Tetra elements to fill the volume.  The process is as follows:

  • Generate a surface mesh of shell elements
  • Check quality and connectivity of the plate elements
  • Generate the tetrahedral mesh
  • Delete the original  surface mesh
  • Edit if necessary to obtain good quality

The standard method of Tetra Meshing can be found through the Mesh > Create > Tetra Mesh pull-down menu and then select the Tetra mesh subpanel.


    • Requirements for the shell mesh:
    • There can be no duplicates in the mesh.
    • Elements should not fold over and overlap each other.
    • Avoid very low minimum tria angles.
    • Avoid a large difference in size between adjacent elements.
    • Avoid a large difference in size between two sides of a wall thickness.
    • For quad elements in the shell mesh:
    • Split quads into 2 trias and create tetra elements under them

- OR –

    • Keep the quad element and create pyramids under them

When using the Standard Tetramesh, the user will select the trias/quads that will define the mesh and optionally the user can select fixed trias/quads. HyperMesh will, when creating the tetra mesh, flip the diagonal of the 2D elements if it deems the resulting tetra mesh will be of a higher quality with the flip.  HyperMesh will not do this to elements selected in the fixed selection. 

  • Floatable Trias/Quads
    • Adjacent tria faces on the tetrahedral mesh may have their diagonal reversed from the shell mesh if tetras are better quality

  • Fixed Trias/Quads:
    • Adjacent tria faces on the tetrahedral mesh always match the shell mesh