You can specify some elements to be fixed, and others to be floatable.
A fixed tria-quad element is one that must be exactly represented as a face of a
tetra/penta-pyramid/hexa element in the final mesh. A floatable element is one whose
nodes locations are used, but the exact connectivity of those nodes can be modified
if it produces a better mesh. Unless you need a special mesh type, such as surface
layers of pentas/hexas, you should select as fixed only those elements that must
match a pre-existing mesh, leaving the rest floatable. If the bounding surface
contains quad elements, and if these quad elements are defined as fixedelements,
then a first layer of elements is generated on the boundary, and pyramid elements
are generated from the quad faces. However, when quad elements are defined as float
elements, they are split into two trias, and the tetra meshing proceeds
normally.
You can also specify various growth options in order to control the tradeoff between
the number of tetras generated and their quality. Higher, more aggressive growth
rates produce fewer elements, but they may be of poorer quality.
In the Tetramesh panel you can choose from three different mesh generation
priorities. The generate mesh normally option applies in most cases, but if your
solver is particularly sensitive to element quality, use the optimize element
quality option. This directs the tetramesher to spend more time trying to generate
better quality elements. In particular, it employs the volumetric ratio (CFD "skew")
measurement for rating potential tetras. For some applications, element quality
considerations are less important than mesh generation time. In those cases, choose
the optimize meshing speed option.
From the 3D page, click Tetramesh.
Access different types of tetra meshing from the subpanels.
Table 1.
Subpanel
Description
Tetra mesh
Fills an arbitrary volume, defined by its surface using
tria/quad elements, with tetrahedral elements.
Tetra remesh
Regenerates the mesh for a single volume of tetrahedral
elements.
Volume tetra
Given a solid entity or a set of surfaces representing a
closed volume, this meshing option generates a shell mesh
and fills the enclosed volume with solid elements. You can
choose to create a shell mesh (2D) using quads, trias, or
mixed elements and a solid mesh (3D) using tetrahedral
elements only or mixed (tetras and penta) elements. In
addition, you can use proximity meshing, which refines the
mesh in areas where the features are small and closer
together. Figure 1.
You can also use surface curvature as a function of
element density as shown below. This option creates finer
mesh in areas of high surface curvature. Figure 2.
When you select quads or mixed as your 2D element
type, HyperMesh creates quad
elements and splits them diagonally into two trias during
tetra face creation. This can create tetra elements whose
triangular faces are right triangles (90-45-45 angles)
instead of equilateral triangles (60-60-60 angles). Figure 3.
Note: Sometimes the meshing may fail to correctly
interpolate from the surface mesh; when this occurs, the
shell elements are cleaned up according to the same
settings used in the Quick TetraMesh macro on the
Utility menu, and a second
attempt is made. This means that some of the features in
a model may be smoothed over.
Tetramesh parameters
Sets general qualities of the tetrameshing engine, such
as a maximum element size, growth rate, the balance between
speed and element quality, or whether to perform smoothing
operations after initial meshing.
Refinement box
Lets you define a specific box-shaped volume within an
existing teramesh in which to generate finer mesh.
