The Topology Checking control determines whether the mesher performs topology checks during patch independent meshing (p. 3) operations and subsequent preprocessing, where the additional preprocessing may include scoping of objects (such as loads, boundary conditions, Named Selections, and so on) to geometry (bodies, faces, edges, and vertices). When these objects are scoped to geometry,
they instruct the mesher to respect those geometry features; thus, the geometry features in these cases are called "protected topology."
If Topology Checking is set to No (default):
• During meshing, patch independent mesh methods attempt to capture protected topology, but may not be able to do so if mesh sizes (element sizes and/or defeature sizes) are too coarse to capture the features, or if the mesher has to ignore features due to mapping or other constraints.
• At the end of meshing, topology checks that would otherwise ensure proper association of mesh to protected topology are skipped.
• After meshing, if you scope an object to geometry, the associated mesh is scoped, too. However, the software does not check to ensure that the mesh is associated to the topology properly, so you must validate the associations manually if you have concerns.
If Topology Checking is set to Yes:
• During meshing, patch independent mesh methods attempt to capture protected topology, but may not be able to do so if mesh sizes (element sizes and/or defeature sizes) are too coarse to capture the features, or if the mesher has to ignore features due to mapping or other constraints.
• At the end of meshing, topology checks that ensure proper association of mesh to protected topology are run. If the mesh is not associated properly, error messages are issued. The topology checking beha-vior differs slightly depending on mesh method and is often stricter than necessary.
• After meshing, if you scope an object to geometry, the associated mesh is scoped, too. In this case, the mesh goes out-of-date, because the state manager must revalidate that all scoped topology is associated properly as protected topology. If you then attempt to re-mesh, the software runs the topology checks and ensures all protected topology is respected. If the topology checks are successful, the mesh is val-idated but not re-meshed. If the topology checks are unsuccessful, the software re-meshes the geometry, treating the newly scoped objects as protected topology.
The following mesh methods support the Topology Checking control:
• Patch Independent Tetra (p. 172)
• MultiZone (p. 196)
• MultiZone Quad/Tri (p. 205)
• Quadrilateral Dominant (p. 205)
• Triangles (p. 205) Note
• Assembly meshing (p. 299) does not support the Topology Checking control.
• If you use the MultiZone mesh method and set Preserve Boundaries (p. 196) to All, the Mul-tiZone method behaves in a patch conforming (p. 2) way, and topology checks are skipped regardless of whether Topology Checking is set to Yes or No.
• If you enable the Use MultiZone for Sweepable Bodies (p. 252) option, MultiZone behaves in a more patch conforming (p. 2) way, and topology checks are skipped regardless of whether Topology Checking is set to Yes or No.
• You can override the default of the Topology Checking control by setting the Topology Checking option on the Options panel (p. 251).
The following figure shows a case where Topology Checking is enabled (Yes) and the meshing fails because a contact region does not have a properly associated mesh. If Topology Checking is disabled (No) for this model, the mesh will not fail and the mesh can be validated manually.
Figure 74: Mesh Failure Due to Topology Checking
You could also solve this model by reducing the mesh size so the mesher can capture the features. But if you scope any new object to geometry, the respected topologies would need to be updated (the mesh does not necessarily have to be regenerated). However, if you then update the mesh and disable Topology Checking, the mesh state will no longer change if you add new scoping. You can plot elements attached to a Named Selection to validate that the mesh is associated properly.
Figure 75: Successful Mesh with Topology Checking Disabled
Pinch
The Pinch feature lets you remove small features (such as short edges and narrow regions) at the mesh level in order to generate better quality elements around those features. The Pinch feature provides an alternative to Virtual Topology (p. 421), which works at the geometry level. The two features work in conjunction with one another to simplify meshing constraints due to small features in a model that would otherwise make it difficult to obtain a satisfactory mesh.
When Pinch controls are defined, the small features in the model that meet the criteria established by the controls will be “pinched out,” thereby removing the features from the mesh. You can instruct the Meshing application to automatically (p. 161) create pinch controls based on settings that you specify, or you can manually (p. 240) designate the entities to be pinched. Pinch controls can be applied to solid and shell models, with certain restrictions as shown in the table below.
The Pinch feature is supported for the following mesh methods:
Volume Meshing:
• Patch Conforming (p. 171)
• Thin Solid Sweeping (p. 194)
• Hex Dominant Meshing (p. 192) Surface Meshing:
• Quad Dominant (p. 205)
• All Triangles (p. 205)
• MultiZone Quad/Tri (p. 205)
The table below shows the types of model (solid or shell), mesh methods, pinch creation methods (auto or manual), and pinch behaviors that are supported for each type of pinch control.
Note
With ANSYS Workbench Release 16.0, post pinch behaviors are migrated into Mesh Connec-tions. When you regenerate a mesh that was created using Pinch Behavior settings, the new mesh might report different results than the previous mesh.
Pinch Creation