2.6 Group Commands

The following commands are available on the Geometry/Group subpad.

2.6.1 Create Group

The Create Group command allows you to create groups of topological entities.

Overview

To create a group, you must specify a list of existing topological entities that constitute members of the group. Available entities include vertices, edges, faces, volumes, and other groups. You can also explicitly include or exclude from the new group one or more lower-topology components associated with any or all members of the group.

Including and Excluding Lower Topology

When you add an entity to a group, GAMBIT implicitly includes in the group all lower topology associated with the entity. For example, if you add a face to a group, GAMBIT implicitly includes in the group the edges and vertices associated with the face.

For any group member other than a vertex, GAMBIT allows you to explicitly include or exclude lower-topology components of the entity. For example, it is possible to create a group that includes a specified face but explicitly excludes all but one of the vertices associated with the face.

GAMBIT provides the following four options for explicitly including or excluding lower topology associated with an entity that is a member of a group:

• Include all lower topology
• Include selected lower-topology components
• Exclude all lower topology
• Exclude selected lower-topology components

The first three options listed above are available directly by means of Edit Lower Topology forms, such as that shown in Figure 2-114.

Figure 2-114: Example Edit Lower Topology form

To execute the fourth option, you must perform the following steps.

1. Use the appropriate Edit Lower Topology form to include all lower-topology components of the specified type
2. Delete from the group list only those components to be excluded from the created group

As an example of the procedure outlined above, consider a case in which a single edge, labeled edge.4, is to be added to a group but one of its two endpoint vertices, labeled vertex.7, is to be excluded from the group. The following procedure outlines the steps necessary to include edge.4 and exclude vertex.7 from the group.

1. Open the Create Group form.
2. Add edge.4 to the list of entities comprising the group.
3. Open the Edit Edge Lower Topology form (see below).
4. Specify the Include all vertices option, and click Apply.
5. Close the Edit Edge Lower Topology form.
6. Delete vertex.7 from the entity list displayed on the Create Group form.

The Effect of Excluding Lower Topology

The primary purpose of excluding lower topology from members of a group is to customize the application of boundary zone types. If you specify a boundary condition for a group, GAMBIT applies the boundary condition to all entities that are members of the group but are not explicitly excluded from the group. For example, it is possible to apply a "wall" boundary condition to three sides of a four-sided face so that the fourth side can be treated as a "free surface."

The exclusion of lower topology from members of a group does not affect group meshing operations. For example, if you mesh a group that includes a face one edge of which is explicitly excluded from the group, GAMBIT grades and meshes the edge when it meshes the face.

Using the Create Group Form

To open the Create Group form (see below), click the Create Group command button on the Geometry/Group subpad.

The Create Group form includes the following specifications.

Using Edit Lower Topology Forms

Edit Lower Topology forms allow you to explicitly include or exclude lower-topology components associated with entities that comprise members of the created group. There are four types of Edit Lower Topology forms:

• Edit Edge Lower Topology
• Edit Face Lower Topology
• Edit Volume Lower Topology
• Edit Group Lower Topology

The following sections describe the specifications available on each of the forms listed above.

Using the Edit Edge Lower Topology Form

To open the Edit Edge Lower Topology form (see below), highlight an edge label in the Create Group form entity list, and click the Edit command button.

The Edit Edge Lower Topology form includes the following specifications.

Using the Edit Face Lower Topology Form

To open the Edit Face Lower Topology form (see below), highlight a face label in the Create Group form entity list, and click the Edit command button.

The Edit Face Lower Topology form includes the following specifications.

Using the Edit Volume Lower Topology Form

To open the Edit Volume Lower Topology form (see below), highlight a volume label in the Create Group form entity list, and click the Edit command button.

The Edit Volume Lower Topology form includes the following specifications.

Using the Edit Group Lower Topology Form

To open the Edit Group Lower Topology form (see below), highlight a group label in the Create Group form entity list, and click the Edit command button.

The Edit Group Lower Topology form includes the following specifications.

2.6.2 Modify Group

The Modify Group command allows you to modify the population of entities within an existing group.

Using the Modify Group Form

To open the Modify Group form (see below), click the Modify Group command button on the Geometry/Group subpad.

The Modify Group form includes the following specifications.

2.6.3 Modify Group Color/Label

The Modify Group Color/Label command button allows you to perform two operations.

The following sections describe the procedures and specifications required to execute the operations listed above.

Modify Group Color

The Modify Group Color command allows you to change the displayed color of the geometry and/or mesh and/or shading associated with one or more groups.

Using the Modify Group Color Form

To open the Modify Group Color form (see below), click the Modify Color command button on the Geometry/Group subpad.

The Modify Group Color form includes the following specifications.

For specific instructions on setting the Geometry or Mesh colors, see Section 2.2.4.

Modify Group Label

The Modify Group Label command allows you to change the label associated with any group.

Using the Modify Group Label Form

To open the Modify Group Label form (see below), click the Modify Label command button on the Geometry/Group subpad.

The Modify Group Label form includes the following specifications.

2.6.4 Move/Copy/Align Groups

The Move/Copy/Align Groups command button allows you to perform the following operations.

The following sections describe the procedures and specifications required to execute the operations listed above.

Move/Copy Groups

The Move/Copy Groups command allows you to reposition and/or reorient one or more groups or to create copies of groups. For a general description of the procedures and specifications required to move and/or copy entities, see "Moving an Entity" and "Copying an Entity," respectively, in Section 2.1.4.

Using the Move/Copy Groups Form

To open the Move/Copy Groups form (see below), click the Move/Copy command button on the Geometry/Group subpad.

For a complete description of the specifications available on the Move/Copy Groups form, see "Using Move/Copy Forms" in Section 2.1.4.

Align Groups

The Align Groups command allows you to reposition and/or reorient a group so that it is aligned with a plane defined by three existing vertices. (For a general description of the procedure and specifications required to align an entity, see "Aligning an Entity," in Section 2.1.4.) When you translate a group using the Align Groups form, GAMBIT translates all vertices, edges, faces, and volumes that constitute parts of the group.

Using the Align Groups Form

To open the Align Groups form (see below), click the Align command button on the Geometry/Groups subpad.

For a complete description of the specifications available on the Align Groups form, see "Using Align Forms" in Section 2.1.4.

2.6.5 Summarize/Check/Query Groups and Total Entities

The Summarize/Check/Query Groups and Total Entities command button allows you to perform the following operations.

The following sections describe the procedures and specifications required to execute the operations listed above.

Summarize Groups

The Summarize Groups command displays group summary information in the Transcript window.

Using the Summarize Groups Form

To open the Summarize Groups form (see below), click the Summarize command button on the Geometry/Group subpad.

The Summarize Groups form includes the following specifications.

Check Groups

The Check Groups command assesses the topological and/or geometrical validity of entity groups and subgroups in the model and summarizes the results in the Transcript window.

When you execute the Check Groups command, GAMBIT checks the model to determine its validity with respect to either or both of the following types of characteristics:

• Topology
• Geometry

Topology refers to the spatial relationships between entities. Geometry refers to proximity and shape characteristics of the model.

Topology Check

Topological validity is an assessment of the underlying organization of the model-for example, the correct associations between a face entity and the edges that comprise its boundaries or between entities that are associated with each other by virtue of a virtual-geometry, guest-host relationship.

For a given group, the Check Groups topology operation examines all entities in the group according to the individual check criteria that are applicable to each entity type. For descriptions of such criteria for vertices, edges, faces, and volumes, see Sections 2.2.7, 2.3.6, 2.4.8, and 2.5.9, respectively.

Geometry Check

Geometrical validity is an assessment of the model with respect to proximity and shape characteristics-such as the distances between connected edges and/or the mathematical continuity of model curves and surfaces. For a given group, the Check Groups topology operation examines all entities in the group according to the check criteria that are applicable to each entity type. For descriptions of such criteria for vertices, edges, faces, and volumes, see Sections 2.2.7, 2.3.6, 2.4.8, and 2.5.9, respectively.

Using the Check Groups Form

To open the Check Groups form (see below), click the Check command button on the Geometry/Group subpad.

The Check Groups form includes the following specifications.

Groups	specifies the groups to be included in the checking operations.
All Pick	All specifies all groups in the model. Pick specifies groups selected by means of the Groups list box. (NOTE: If you pick a group in the graphics window or click in the Groups list box, GAMBIT automatically selects the Pick option.)
Check Topology	specifies a topology check on the selected groups.
Check Geometry	specifies a geomtery check on the selected groups.

Query Groups

The Query Groups command allows you to identify the locations and/or the names of specific groups.

Using the Query Groups Form

To open the Query Groups form (see below), click the Query command button on the Geometry/Group subpad.

For a general description of using the Query Groups form, see "Using the Query Vertices Form" in Section 2.2.7, above.

Total Entities

The Total Entities command displays in the Transcript window the total number of geometry and/or mesh entities that currently exist in the model. For example, if you select only the Geometry entities option on the Total Entities form and click Apply, GAMBIT displays in the Transcript window the total numbers of vertices, edges, faces, volumes, groups, and coordinate systems that currently exist in the model.

Using the Total Entities Form

For a description of the options available on the Total Entities form, see "Total Entities," in Section 2.2.7.

2.6.6 Delete Groups

The Delete Groups command deletes one or more groups from the model.

Deleting Group Member Entities

When you delete a group, GAMBIT disassociates its member entities and deletes the group label, thereby removing the group from the list of available groups. In doing so, GAMBIT retains or deletes the member entities of the group according to the following rules.

• If you delete a group and do not select the Lower topology option, GAMBIT does not delete its member entities from the model.
• If you select the Lower topology option when deleting a group, GAMBIT deletes all member entities that do not constitute parts of higher-topology entities.

As an example of the first rule, consider a group labeled group.3 that consists of two faces, labeled face.7 and face.18. If you delete group.3 and do not select the Lower topology option, GAMBIT disassociates group.3 and removes it from the list of available groups but does not delete either face.7 or face.18 from the model.

As an example of the second rule, consider a group labeled group.1 that consists of the following members: edge.3, edge.6, edge.9, face.2, and face.8. Furthermore, assume the following.

• edge.3 and edge.6 constitute parts of face.2
• face.2 does not constitute part of any volume
• edge.9 constitutes one side of a face that is not a member of group.1
• face.8 constitutes part of a volume that is not a member of group.1

If you delete group.1 and select the Lower topology option, GAMBIT disassociates group.1 and deletes face.2, including edge.3 and edge.6, but does not delete edge.9 or face.8.

Deleting Virtual Groups

Using the Delete Groups Form

To open the Delete Groups form (see below), click the Delete command button on the Geometry/Group subpad.

The Delete Groups form includes the following specifications.

© Fluent, Inc. 12/10/01