Mesh Parameters

Basic Mesh Parameters

Parameters in the Mesh section provide the basic definition of the mesh, such as element size and order.

Parameter

Availability

Description

Shape

Surface quad and sweep meshes

Surface quad meshes:

Quads Dominant to mesh the surface with quadrangle elements when it is possible and allow triangle elements in transition regions,
Quads Only to mesh the surface with quadrangle elements exclusively, or
Quads Minimum to mesh primarily with triangle elements and use a minimum of quadrangle elements.

When you select Quads Only, model geometry might require the inclusion of some triangle elements to complete the mesh. To reduce the potential for creating triangle elements, create each component of the mesh boundary with an even number of nodes.

Warning: In some cases, selecting Quads Only might result in a poor or invalid mesh or fail to create a mesh. Mesh boundaries that include acute angles or inconsistent node distributions are two potential causes of problems.

Sweep meshes:
- Hex Dominant to mesh the solid with hexahedral elements when it is possible and to allow tetrahedral, pyramid, or prismatic elements in transition regions, or
- Hex Only to mesh the solid with hexahedral elements exclusively.

Element order

All

Linear or Quadratic.

Midside nodes on geometry

Surface triangle and Tetrahedron meshes

Select to constrain midside nodes of quadratic elements to the support.

Mesh size

All

Specify a mesh size. The specified size is an approximation that Mesh Creation applies wherever possible.

Map

Surface triangle and surface quad meshes

Mapped meshing is used by default for surface triangle meshes and surface quad meshes. Deactivate it (use a free mesh) to smooth mesh transitions and provide a mesh with elements whose size is closer to the user-defined mesh size.

Map mesh the surfaces

Tetrahedron meshes

Mapped meshing is used by default for the surface mesh used to generate tetrahedron meshes on a volume; deactivate it (use a free mesh) to smooth mesh transitions.

Mapped meshing is not applied once the surface portion of creating a tetrahedron mesh is complete.

Minimize triangles in transition

Surface quad meshes

Enabled by default, creates a mesh that favors quad elements instead of triangles. Engineers prefer quad elements for most structural simulations. Simulations using quad elements are more accurate and achieve better convergence. However, quad elements are distorted or possibly invalid when fit to some geometry shapes. As a result, this kind of mesh creates rougher transitions between mesh regions.

If you deactivate this option, Mesh Creation preferentially replaces the distorted quad elements with triangles and the transitions between regions of the mesh are smoother (below right).

The smoother mesh is the superior mesh transition. Meshes with superior mesh transitions are better for high-speed, low duration high-energy events.

Minimal mesh

Beam meshes

Creates a single mesh (beam) segment between two vertices instead of multiple segments based on the mesh size.

Layers distribution

Sweep meshes only

Specify how the mesh layer thickness varies through the depth of the sweep. Use one of the following:

Uniform to use the same layer thickness throughout the part, when the part is extruded along a straight line. When a part is extruded along a curved line, the resulting layers do not have a uniform thickness.
Arithmetic to change the thickness using an arithmetic progression using the Layer size ratio.
Geometric to change the thickness using a geometric progression using the Layer size ratio.

Number of layers

Sweep meshes only

The number of element layers created between the source and target faces.

Layer size (or First layer size)

Sweep meshes only

The layer size is the thickness of all layers in a uniform sweep distribution. The first layer size is the starting size of the progression for an arithmetic or geometric distribution.

Layer size ratio

Sweep meshes only, with arithmetic or geometric layer distribution

The layer size ratio is the progression constant for an arithmetic or geometric layer distribution.

Symmetric layers

Sweep meshes only, with arithmetic or geometric layer distribution

Apply symmetry to the source and target faces so the layer progression starts at both ends and ends in the center of the sweep.

Global interior size

Octree tetrahedron meshes only

Specify a maximum size for interior elements.

Absolute sag and Proportional sag

Octree triangle, Octree

The absolute sag is the maximum gap between the mesh and the geometry. The proportional sag is the ratio between the local absolute sag and the length of the local mesh edge.

Important: Proportional sag value= (local Absolute sag value) / (local mesh edge length value)

You can specify both absolute sag and proportional sag; the value that allows less sag is used.

Minimum size

All Octree triangle, Octree tetrahedron, tetrahedron, and surface triangle mesh tetrahedron, tetrahedron, and surface triangle meshes, with either absolute or proportional sag

Specify the element size limit for mesh refinement because of the sag specifications. Use the context menu to remove the default formula (based on the mesh size), and enter a value.

Mesh edge removal

Octree triangle and Octree tetrahedron meshes

Specify an edge size below which small edges are removed after meshing.

Warning: This operation can violate other mesh constraints.

Multiple elements across narrow regions

Octree triangle and Octree tetrahedron meshes

Generate a mesh with at least two element layers in thin model areas. To create the extra layers, all mesh edges that satisfy one of the following conditions are split automatically:

A mesh edge on a curve connecting two nodes on vertices.
A mesh edge on a face connecting two nodes on curves or vertices.
A mesh edge inside a volume connecting two surface nodes.

Note: Applying multiple elements across narrow regions might decrease the mesh quality in areas with small geometry (small edges or thin faces).

Narrow region treatment

Tetrahedron meshes

Specify a narrow region treatment:

None: Do not modify the mesh in narrow regions.
Split tets: Split tetrahedrons to create layers through the thickness of narrow regions without changing the surface mesh. This option is useful in structural simulations, when you require added layers to provide stiffness.
Refine surface: Insert nodes in the surface mesh (local mesh refinement) to increase the mesh density in narrow regions. Refining the surface mesh creates many more elements than splitting tetrahedrons and is helpful where a smooth mesh throughout the narrow region is important, such as for computational fluid dynamics. You can specify a Minimum number of layers for the refined areas.

Minimum number of layers

Surface triangle meshes and Tetrahedron meshes where Refine surface is selected for the Narrow region treatment

Specify the minimum number of element layers for narrow model regions.

Growth ratio on surface

Tetrahedron, surface triangle, and surface quad meshes

Specify the maximum amount (multiplier) by which adjacent surface elements can differ in size. The growth ratio controls the smoothness of mesh size transitions. The default ratio is 1.41.

Growth ratio in volume

Tetrahedron meshes only

Specify the maximum amount by which adjacent elements through the volume can differ in size. The growth ratio controls the smoothness of mesh size transitions. The default volumetric ratio is 1.41 (no change allowed).

Geometry Parameters

Parameters in the Geometry section describe the level of dependence of the mesh on the underlying geometry.

Geometry parameters are available for tetrahedron, sweep, surface triangle, and surface quad meshes.


Parameter	Description
Angle between faces	Specify the minimum angle between faces to constrain the common edge (the angle is computed between the normals of the neighboring faces). If the angle between two faces is less than the specified value, Mesh Creation groups these faces together.
Angle between curves	Specify the minimum angle between curves to constrain the common vertex.
Curvature angle	Specify the minimum fillet angle to consider for constraining the boundary edges of a fillet. If the rotational angle of a fillet is greater than the curvature angle, Mesh Creationconstrains the faces along the fillet edges.
Simplify geometry under	Specify the minimum size of topological edges to retain in the mesh. Smaller geometry is ignored to simplify the mesh. Whenever possible, Mesh Creationmerges edges if the topological edges are smaller than the specified value or if the distance between two edges is less than the specified value. Notes: The default value is specified by a predefined formula; use the context menu options to remove the formula and edit the value directly. Simplification runs automatically. Changing the value results in a new run and can invalidate other edits to the mesh. Deleting the value results in no simplification. Consider the following geometry: Simplification when the value is less than the distance between the parallel edges: Simplification when the value is greater than the distance between the parallel edges:
Remove logos	Activate this option and enter a Maximum height and a Maximum size to remove small features such as logos. Notes: The default values are specified by a formula; use the context menu options to remove the formula and allow editing. Logos are not considered for removal if their height or depth from the surrounding surface is greater than the Maximum height or if their diagonal measurement is greater than the Maximum size.

Quality Parameters

Parameters in the Quality section describe the element quality parameters used to control mesh generation. Full definitions of the mesh quality criteria are available from the Quality Criteria dialog box, located with the Quality Analysis tools in the Check section of the action bar.


Parameter	Availability	Description
Smoothing criteria	Octree triangle and Octree tetrahedron meshes	Select Shape factor, Skewness, or Stretch to determine the dominant element quality factor when creating the mesh. Shape factor is the default.
Intermediate nodes on geometry	Octree meshes with a quadratic element order	The distance, d, between the geometry and the intermediate nodes is a function of the Jacobian and Warp quality criteria.
Shape factor	Surface triangle meshes	The ratio of the actual surface area of an element to the area based on the ideal edge length. For example, an equilateral triangle. The best ratios approach `1`.
Aspect ratio	Surface triangle meshes	The ratio of the longest to shortest element edge within any single element. The best ratios approach `1`.
Minimal/Maximal Length	Surface quad and sweep meshes	The minimum or maximum element edge length, based on conformance to the mesh size.
Minimal/Maximal Angle tria	Surface quad and sweep meshes	The minimum or maximum allowed angle for triangular elements. The best elements have all angles near 60°.
Minimal/Maximal Angle quad	Surface quad and sweep meshes	The minimum or maximum allowed angle for a quad element. The best elements have all angles near 90°.
Warp angle	Surface quad and sweep meshes	Warping of the element out of the expected planar surface.
Jacobian	Surface triangle and surface quad meshes with linear element order, quadratic element order, and all sweep meshes	The ratio of the minimum Jacobian for all points in an element to the maximum Jacobian. The best ratios approach `1`.

Maximum Nodal Deviation Parameters

Parameters in the Maximum Nodal Deviation section define the distance by which the mesh nodes might be offset from features. Displaced nodes remain associated with the original geometric features and move only when movement improves mesh quality. Nodal deviation is available only for surface triangle and surface quad meshes.

You can also allow nodes to move when optimizing a mesh. For more information, see Optimizing Elements in a Surface Mesh.


Parameter	Description
From constraints	Allow nodes to move away from their associated vertices or edges, while remaining within the boundaries of an existing surface.
From geometry	Allow nodes to move along the surface normal. When used with From constraints, displacements within the surface are applied first. Displacements normal to the surface are applied only if they further improve mesh quality. Normal displacements can flatten warped quadrangle elements instead of requiring them to split into triangular elements.
From free edges	Allow nodes to move tangentially away from free edges.

Feature Parameters

Parameters in the Feature section define special mesh generation around recognized shapes such as holes.

Note: Select

to edit the feature parameters in a separate Features list dialog box. The Features List dialog box contains tabs for each feature type listed in the table. You can edit, remove, or deactivate the rule from the dialog box.


Parameter	Availability	Description
2D Holes	Surface triangle and surface quad meshes	Specify 2D hole sizes to be removed (ignored by the mesh) or meshed around. For more information, see Defining a Rule to Remove 2D Holesand Defining a Rule to Mesh Around 2D Holes, respectively.
3D Holes	Tetrahedron, surface triangle, surface quad, and sweep meshes	Specify 3D hole sizes to be removed (ignored by the mesh) or meshed around. For more information, see Defining a Rule to Remove 3D Holes and Defining a Rule to Mesh 3D Holes, respectively.
Fillets	Tetrahedron, surface triangle, surface quad, and sweep meshes	Define a rule to impose a number of layers to mesh fillets. For more information, see Defining a Rule to Mesh Fillets.
Beads	Surface triangle and surface quad meshes	Specify bead sizes to be removed (ignored by the mesh) or meshed. For more information, see Defining a Rule to Remove Beads and Defining a Rule to Mesh Beads, respectively.
Flange Holes	Surface triangle and surface quad meshes	Specify flange hole sizes to be removed (ignored by the mesh) or meshed. For more information, see Flange Holes.