Cubit
15.8 *User
Documentation*

CUBIT provides several options for controlling the density of a mesh by adapting to various geometric, analysis, or user-defined properties. Interval sizes are defined automatically, explicitly, or through *sizing functions*. The sizing functions can be based on the physical features of the model, a previous analysis solution, or a user-specified bias. Adaptivity can apply to meshing either curves or surfaces.

CUBIT provides several ways to adaptively mesh curves. Three curve meshing schemes are provided for this purpose. They include the following schemes:

The first two schemes use characteristics of the geometric model to define element sizes. The third scheme uses a field function typically defined from a previous analysis solution. FeatureSize is an alpha feature and should be used with caution.

Adaptive surface meshing in CUBIT produces a function following mesh which sizes elements based on the value of the driving function at the spatial location at which the element is to be placed. Adaptive surface meshing is performed using the paving, triadvance or tridelaunay algorithms in combination with an appropriate sizing function. The types of sizing functions that can be used are

- Bias Sizing
- Constant Sizing
- Curvature Sizing
- Linear Sizing
- Interval Sizing
- Inverse Sizing
- Super Sizing
- Test Sizing
- Exodus-based field function
- Geometry Adaptive (Skeleton Sizing)
- Geometry Adaptive for TriMesh and TetMesh Schemes

Super sizing and test sizing functions are alpha features and should be used with caution.

The procedure for adaptively meshing a surface is to designate paving, triadvance or tridelaunay as the mesh scheme for that surface, assign sizing function types, and mesh the surface.

The command syntax of these commands is:

Surface < id > Scheme {Pave|TriAdvance|TriDelaunay}then

Import Sizing Function '<exodusII_filename>' Block <block_id> Variable '<variable_name>' Time <time> [Deformed]

Surface <id> Sizing Function [Type] Exodus [Min <min_value> Max <max_value>]or

Surface <id> Sizing Function [Type] {Constant|Curvature|Interval|Inverse|Linear|Super|Test|None}] [Neighbor [<max_neighbors>]]

(See note below regarding 'Neighbor' parameter)or

Surface <id> Sizing Function [Type] Bias Start Curve <id_range> {Finish Curve <id_range>| Factor <val>}then

Mesh Surface <id>

Adaptive volume meshing in CUBIT produces a function following mesh that sizes elements based on the value of the driving function at the spatial location at which the element is to be placed. Adaptive volume meshing is performed using the tetmesh scheme in combination with an appropriate sizing function. The types of sizing functions that can be used are constant, test, geometry adaptive and geometry adaptive (skeleton sizing). Test sizing is an alpha feature and should be used with caution. Other sizing functions will be added in future versions of Cubit.

The procedure for adaptively meshing a volume is to designate **tetmesh** as the mesh scheme for that volume, assign sizing function types, and mesh the volume.

The command syntax of these commands is:

Volume <id> scheme tetmesh

Volume <id> Sizing Function [Type] {Constant|Test|None}

Mesh Surface <id>

The following sections describe details of the various volume sizing methods.

- Constant Sizing
- Test Sizing
- Geometry Adaptive (Skeleton Sizing)
- Geometry Adaptive for TriMesh and TetMesh Schemes

Note regarding 'Neighbor' parameter:

The maximum neighbors is the number of points used by the sizing function to compute the size at the requested point. If the number of neighbors is zero, all of the points on the boundary are used in the size calculation. If the number of neighbors is some other number, only that number of closest points are used in the calculation.