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4. SPECIFYING ZONE TYPES

4.1 Overview

Zone-type specifications define the physical and operational characteristics of the model at its boundaries and within specific regions of its domain. There are two classes of zone-type specifications:

Boundary-type specifications, such as WALL or VENT, define the characteristics of the model at its external or internal boundaries. Continuum-type specifications, such as FLUID or SOLID, define the characteristics of the model within specified regions of its domain.

The following sections briefly describe boundary-type and continuum-type specifications and illustrate their purposes in the definition of an example computational model involving simple geometry.


4.1.1 Boundary Type Specifications

Boundary-type specifications define the physical and operational characteristics of the model at those topological entities that represent model boundaries. For example, if you assign an INFLOW boundary type specification to a face entity that is part of three-dimensional model, the model is defined such that material flows into the model domain through the specified face. Likewise, if you specify a SYMMETRY boundary type to an edge entity that is part of a two-dimensional model, the model is defined such that flow, temperature, and pressure gradients are identically zero along the specified edge. As a result, physical conditions in the regions immediately adjacent to either side of the edge are identical to each other.

NOTE: To apply a "periodic" boundary condition for use with a FLUENT solver, you must first create a mesh hard link between the pair of edges (2-D) or faces (3-D) to which the boundary condition is to apply. (For a description of mesh hard links, see Section 3.2.3.) In addition, you must assign a PERIODIC boundary type to both edges (or faces) in the pair, and both edges (or faces) must constitute members of a single entity set. (See Figure 4-1.)

Figure 4-1: Periodic boundary condition specifications—FLUENT solver

For a complete description of the procedures required to specify boundary types, see Section 4.2.1, below.


4.1.2 Continuum Type Specifications

Continuum-type specifications define the physical characteristics of the model within specified regions of its domain. For example, if you assign a FLUID continuum-type specification to a volume entity, the model is defined such that equations of momentum, continuity, and species transport apply at mesh nodes or cells that exist within the volume. Conversely, if you assign a SOLID continuum-type specification to a volume entity, only the energy and species transport equations (without convection) apply at the mesh nodes or cells that exist within the volume.


4.1.3 The Effect of Zone Type Specifications

As an example of the effect of zone-type specifications on the specification of a computational model, consider the geometry shown in Figure 4-2—which consists of a single volume in the shape of a straight, elliptical cylinder. The geometry includes one volume, three faces, two edges, and two vertices.

Figure 4-2: Boundary- and continuum-type specifications

The geometry shown in Figure 4-2 can be used to model many different types of transport problems, including fluid flow through a straight, elliptical pipe and heat conduction through a solid, elliptical rod. Table 4-1 and Table 4-2 show the zone-type specifications associated with the fluid flow and heat conduction problems, respectively.

Table 4-1: Fluid flow problem, zone-type specifications

Entity Zone Zone Type
face.1 Boundary WALL
face.2 Boundary INFLOW
face.3 Boundary OUTFLOW
volume.1 Continuum FLUID

Table 4-2: Heat conduction problem, zone-type specifications

Entity Zone Zone Type
face.1 Boundary WALL
volume.1 Continuum SOLID

NOTE: Computational solvers differ from each other in the manner in which they utilize boundary-type and continuum-type specifications. For descriptions of the use of boundary- and continuum-type specifications that are available in a specific solver, consult the solver documentation.


4.2 Zones Commands

When you click the Zones command button on the Operation toolpad, GAMBIT opens the Zones subpad. The Zones subpad contains command buttons that allow you to add, modify, and delete boundary- and continuum-type specifications. The symbols associated with each of the Zones subpad commands are as follows.

Symbol Command Description
Specify Boundary Types Allows you to create, modify, and delete boundary-type specifications
Specify Continuum Types Allows you to create, modify, and delete continuum-type specifications

The following sections of this chapter describe each of the Zones commands listed above.


4.2.1 Specify Boundary Types

The Specify Boundary Types operation (physics create btype, physics modify btype, and physics delete btype commands) creates, modifies, or deletes boundary-type specifications for topological entities that represent model boundaries. The Specify Boundary Types form contains the following categories of specification options:

The Action options specify the type of operation to be performed by the command. The display options allow you to display labels and/or colors associated with existing boundary-type specifications. The definition options specify the name, type, and entities included in any boundary type.

Specifying the Action

The Specify Boundary Types form provides the following Action options:

To Modify or Delete an existing boundary-type specification, you must select its name in the Name|Type scroll list on the Specify Boundary Types form.

Specifying the Display

The Specify Boundary Types form includes two options that allow you to display labels and/or colors associated with currently specified boundary types:

These options affect the graphics display only while the Specify Boundary Types form is open.

NOTE: The Show colors option displays colored shading for entities associated with boundary types regardless of whether the GAMBIT graphics display is in the wireframe, hidden, or shaded display mode.

Specifying the Color Assignment Mode

GAMBIT assigns colors associated with the Show colors option according to either of two criteria:

You can specify which criterion determines the shading color by means of the GRAPHICS.GENERAL.ZONECOLOR_TYPE default variable, the allowable values of which are as follows. By default, GAMBIT assigns colors according to the boundary-zone type. (NOTE: For instructions regarding the modification of GAMBIT default variables, see Section 4.2.4 of the GAMBIT User's Guide.)

Assigning Colors by Sequential Order

If you set the GRAPHICS.GENERAL.ZONECOLOR_TYPE default variable equal to 0, GAMBIT assigns boundary-zone shading colors according to the sequential order in which the zone assignments are made. Table 4-3 shows the hard-coded associations between sequential order and shading color for GAMBIT boundary-zone assignments.

Table 4-3: Boundary-zone color assignments by order

Order Color
1 red
2 yellow
3 blue
4 magenta
5 cyan
6 white
7 orange
8 pink
9 brown
10 salmon
11 coral
12 purple
13 slateblue
14 sienna
15 deepskyblue
16 khaki
17 skyblue
18 chocolate
19 hotpink
20 firebrick
21 plum
22 orchid
23 maroon
24 lightpink

For example, if you create a boundary-zone specification and assign the WALL boundary type to a given face (before assigning any other boundary types), GAMBIT displays the face with red shading when the Show colors option is on. If you then create a new boundary-zone specification and assign the WALL boundary type to a different face, GAMBIT displays the second face with yellow shading even though its boundary-zone type is identical to that of the first boundary-zone assignment.

Assigning Colors by Boundary-Zone Type

If you set the GRAPHICS.GENERAL.ZONECOLOR_TYPE default variable equal to 1, GAMBIT assigns boundary-zone shading colors according to the boundary-zone type. Table 4-4 shows the hard-coded associations between boundary-zone type and shading color for GAMBIT boundary-zone assign­ments.

Table 4-3: Boundary-zone color assignments by type

Type Color
AXIS yellow
CONJUGATE white
CONVECTION white
CYCLIC cyan
DEAD grey
ELEMENT_SIDE seagreen
ESPECIES white
EXHAUST_FAN red
FAN lightblue
FREE_SURFACE magenta
GAP purple
INFLOW lightblue
INLET lightblue
INLET_VENT lightblue
INTAKE_FAN blue
INTERFACE lightgoldenrod
INTERIOR seagreen
INTERNAL orange
LIVE seagreen
MASS_FLOW_INLET lightblue
MELT magenta
MELT_INTERFACE lightgoldenrod
MEMBRANE orange
MOVING_BOUNDARY white
NODE grey
OUTFLOW red
OUTLET red
OUTLET_VENT brown
PERIODIC cyan
PINTERFACE lightgoldenrod
PLOT white
POROUS orange
POROUS_JUMP orange
PRESSURE red
PRESSURE_FAR_FIELD pink
PRESSURE_INFLOW lightblue
PRESSURE_INLET lightblue
PRESSURE_OUTFLOW red
PRESSURE_OUTLET red
RADIATION orange
RADIATOR orange
RECIRCULATION_INLET lightblue
RECIRCULATION_OUTLET red
SHELL white
SLIP white
SPRING white
SREACTION white
SURFACE magenta
SYMMETRY yellow
TRACTION tan
TRAJECTORY salmon
UNSPECIFIED khaki
VELOCITY lightblue
VELOCITY_INLET lightblue
VENT orange
WALL white

In this case, if you create a boundary-zone specification and assign the WALL boundary type to a given face, GAMBIT displays the face with white shading when the Show colors option is on. If you then create a new boundary-zone specification and assign the WALL boundary type to a different face, GAMBIT also displays the second face with white shading.

Specifying the Definition

To define (create or modify) a boundary-type specification, you must specify the following parameters:

The Name parameter is an overall label that is assigned to the specification. The Type parameter is a solver-specific keyword that represents a physical or operational characteristic, such as WALL or INFLOW. The Entity set consists of one or more topological entities to which the Type specification applies.

Specifying the Name

When you assign a boundary-type specification, you can assign a name to the specification. The name constitutes an overall label for the boundary-type specification. It may consist of any combination of alphanumeric characters and/or symbols that are valid with respect to the solver into which the mesh is to be read.

NOTE: The Polyflow solver imposes special restrictions on boundary and continuum names. Specifically, boundary and continuum names for meshes created for the Polyflow solver must obey the following naming format:

name.number

where name is the boundary or continuum name, and number is a unique number. For example, in a given model, boundary entities can be assigned names such as inflow.1, outflow.2, and wall.3.

Specifying the Type

Each computational solver is associated with a unique set of allowable boundary types. For detailed descriptions of the boundary types that are available for each of the solvers supported by GAMBIT, consult the appropriate solver documentation.

NOTE: If you change solvers after assigning boundary-type specifications, GAMBIT retains only those specifications that are valid with respect to the new solver. For example, if you select the FIDAP solver and assign WALL and SLIP boundary-type specifications, then change to the FLUENT/UNS solver, GAMBIT retains only the WALL boundary-type specification-because the SLIP boundary type is not valid in the FLUENT/UNS solver. If you reselect the FIDAP solver, GAMBIT restores the previous FIDAP-valid boundary-type specifications as well as any new specifications that are valid with respect to the FIDAP solver.

Specifying Entity Sets

Each boundary-type specification must include an entity set. The entity set constitutes one or more topological entities to which the Type specification applies. To add an entity to an entity set, you must specify the following parameters:

The type parameter defines the general type of entity that is to be added to the entity set. The label parameter specifies the name of a specific entity that is to be added to the set.

Specifying the Entity Type

The option button in the Entity section of the Specify Boundary Types form allows you to specify the general type of the entity that is to be added to the entity set. The entity types available for boundary-type specifications include Edges, Faces, and Groups.

If you select the Groups option, GAMBIT displays an Edit command button immediately to the right of the Entity list box. When you click the Edit command button, GAMBIT opens either the Create Group or Modify Group form. The Create Group and Modify Group forms allow you to create or modify, respectively, groups of entities that are to be included in the boundary-type specification entity set. (For a description of the use of the Create Group and Modify Group forms, see Chapter 2 of this guide.)

NOTE: The Entity section of the Specify Boundary Types form contains an option button and a list box that allow you to specify the type and label, respectively, of one or more entities that are to be added to the entity set. The Entity section also contains a scroll list that displays the Label and Type of all entities that currently exist in the entity set.

Specifying the Entity Label

To add an entity to an entity set, you must specify its label. You can specify the label in one of three ways:

Using the Specify Boundary Types Form

To open the Specify Boundary Types form (see below), click the Specify Boundary Types command button on the Zones subpad.

The Specify Boundary Types form contains the following specifications.

Action:
Add creates a new boundary-type specification. To create a new boundary-type specification, input the appropriate Name, Type, and Entity parameters, and click Apply.
Modify modifies an existing boundary-type specification. To select a boundary-type specification for modification, highlight (left-click) its name in the Name|Type scroll list (see below). To modify the boundary-type specification, change the Name, Type, and/or Entity parameters, and click Apply.
Delete deletes an existing boundary-type specification. To select a boundary-type specification for deletion, highlight (left-click) its name in the Name|Type scroll list (see below). To delete the boundary-type specification, click Apply.
Delete all deletes all existing boundary-type specifications.
Name | Type lists the names (Name) and types (Type) of all existing boundary-type specifications.
Show labels displays labels for all currently defined boundary types while the Specify Boundary Types form is open.
Show colors displays colors associated with all currently defined boundary types while the Specify Boundary Types form is open.
Name: specifies the name associated with the current boundary-type specification.
Type:
VENT
WALL
...
specifies the boundary type.

NOTE: Each computational solver is associated with a unique set of available boundary types (see, "Specifying the Type," above).

Entity:
Groups
Faces
Edges
specifies the general type of topological entity to which the boundary type is assigned.

NOTE (1): Boundary-type specifications may include entities of more than one kind. For example, some solvers allow a single boundary-type specification to include edges, faces, and/or volumes.

  NOTE (2): If you specify the Group option, GAMBIT displays a command button, titled Edit, immediately to the right of the Group list box. The Edit command button allows you to create or modify a group that is part of the set of entities that comprise the boundary-type specification.
  • To create a group for inclusion in the boundary-type specification, click Edit.
  • To modify an existing group that is part of the boundary-type specification, highlight the group label in the Entity list (see below) and click Edit.
When you click Edit to create or modify a group, GAMBIT opens either the Create Group or Modify Group forms, respectively. For instructions concerning the use of the Create Group or Modify Group forms, see "Using the Create Group Form" or "Using the Modify Group Form," respectively, in Chapter 3 of this guide.
Groups
Faces
Edges
specifies the entity (or entities) to which the boundary type is assigned.
Label | Type lists the label (Label) and type (Type) of all topological entities currently associated with the current boundary-type specification.
Remove deletes the currently highlighted entity from the list of entities associated with the boundary-type specification.
Edit opens an Edit Lower Topology form, which allows you to specify whether or not lower geometry and/or geometry connected to the currently highlighted entity is included in the boundary-type specification. For instructions in the use of the Edit Lower Topology forms, see "Using Edit Lower Topology Forms" in Chapter 2 of this guide.


4.2.2 Specify Continuum Types

The Specify Continuum Types operation (physics create ctype, physics modify ctype, and physics delete ctype commands) creates, modifies, or deletes continuum-type specifications that define the physical characteristics of the model in any region defined by a set of topological entities. The physical characteristics, in turn, determine which transport equations apply to the problem.

The Specify Continuum Types form contains the following categories of specification options:

The Action options specify the type of operation to be performed by the command. The display options allow you to display labels and/or colors associated with existing continuum-type specifications. The definition options specify the name, type, and entities included in any continuum type.

Specifying the Action

The Specify Continuum Types form provides the following Action options:

To Modify or Delete an existing continuum-type specification, you must select its name in the Name|Type scroll list on the Specify Continuum Types form.

Specifying the Display

The Specify Continuum Types form includes two options that allow you to display labels and/or colors associated with currently specified continuum types:

These options affect the graphics display only while the Specify Boundary Types form is open.

NOTE: The Show colors option displays colored shading for entities associated with continuum types regardless of whether the GAMBIT graphics display is in the wireframe, hidden, or shaded display mode.

Specifying the Color Assignment Mode

GAMBIT assigns colors associated with the Show colors option according to either of two criteria:

You can specify which criterion determines the shading color by means of the GRAPHICS.GENERAL.ZONECOLOR_TYPE default variable, the allowable values of which are as follows. By default, GAMBIT assigns colors according to the continuum type. (NOTE: For instructions regarding the modification of GAMBIT default variables, see Section 4.2.4 of the GAMBIT User's Guide.)

Assigning Colors by Sequential Order

If you set the GRAPHICS.GENERAL.ZONECOLOR_TYPE default variable equal to 0, GAMBIT assigns continuum shading colors according to the sequential order in which the zone assignments are made. The hard-coded associations between sequential order and shading color for GAMBIT continuum assignments are identical to those for boundary-zone assignments (see Table 4-3 in Section 4.2.1, above). For example, if you create a continuum specification and assign the FLUID continuum type to a given volume (before assigning any other continuum types), GAMBIT displays the boundary faces of the volume with red shading when the Show colors option is on. If you then create a new continuum-type specification and assign the FLUID type to a different volume, GAMBIT displays the boundary faces of the second volume with yellow shading even though its continuum type is identical to that of the first continuum assignment.

Assigning Colors by Continuum Type

If you set the GRAPHICS.GENERAL.ZONECOLOR_TYPE default variable equal to 1, GAMBIT assigns continuum shading colors according to the continuum type. Table 4-5 shows the hard-coded associations between continuum type and shading color for GAMBIT continuum assign­ments.

Table 4-5: Continuum color assignments by type

Type Color
CONJUGATE white
DEFORMABLE yellow
FLUID seagreen
POROUS orange
RIGID white
SOLID white
UNSPECIFIED khaki

In this case, if you create a continuum specification and assign the FLUID continuum type to a given volume, GAMBIT displays the volume boundary faces with seagreen shading when the Show colors option is on. If you then create a new continuum-type specification and assign the FLUID boundary type to a different volume, GAMBIT also displays the boundary faces of the second volume with seagreen shading.

Specifying the Definition

To define (create or modify) a continuum-type specification, you must specify the following parameters:

The Name parameter is an overall label that is assigned to the specification. The Type parameter is a solver-specific keyword that represents a physical or operational characteristic, such as WALL or INFLOW. The Entity set consist of one or more topological entities to which the Type specification applies.

Specifying the Name

The specifications for continuum-type Name parameters are identical to those of boundary-type Name parameters, above. (See Section 4.2.1, above.)

Specifying the Type

There are four continuum types, each of which is associated with a set of fundamental transport equations. The four continuum types are as follows:

NOTE: For a detailed description of the equations associated with the continuum types, consult the appropriate solver documentation.

Specifying Entity Sets

The specifications for continuum-type Entity sets are similar to those for boundary-types, above. (See Section 4.2.1, above.) They differ only in that you can assign continuum-type specifications only to Faces, Volumes, and Groups.

Using the Specify Continuum Types Form

To open the Specify Continuum Types form (see below), click the Specify Continuum Types command button on the Zones subpad.

The Specify Continuum Types form contains the following specifications.

Action:
Add creates a new continuum-type specification. To create a new continuum-type specification, input the appropriate Name, Type, and Entity parameters, and click Apply.
Modify modifies an existing continuum-type specification. To select a continuum-type specification for modification, highlight (left-click) its name in the Name|Type scroll list (see below). To modify the continuum-type specification, change the Name, Type, and/or Entity parameters, and click Apply.
Delete deletes an existing continuum-type specification. To select a continuum-type specification for deletion, highlight (left-click) its name in the Name|Type scroll list (see below). To delete the continuum-type specification, click Apply.
Delete all deletes all existing continuum-type specifications.
Name | Type lists the names (Name) and types (Type) of all currently existing continuum-type specifications.
Show labels displays labels for all currently defined continuum types while the Specify Continuum Types form is open.
Show colors displays colors associated with all currently defined continuum types while the Specify Continuum Types form is open.
Name: specifies the name associated with the continuum-type specification.
Type:
FLUID
POROUS
SOLID
Conjugate
specifies the continuum-type.

NOTE: The Conjugate continuum type is  available only for the FLUENT 4 solver.

Entity:
Groups
Volumes
Faces
specifies the general type of topological entity to which the continuum type is assigned.

NOTE (1): The set of topological entities that are associated with a given continuum-type specification can include entities of more than one type. For example, some solvers allow a given continuum-type specification to include one or more groups, volumes, and/or faces.

NOTE (2): If you specify the Group option, GAMBIT displays a command button, titled Edit, immediately to the right of the Group list box. The Edit command button allows you to create or modify a group that is part of the set of entities that comprise the continuum-type specification.

  • To create a group for inclusion in the continuum-type specification, click Edit.
  • To modify an existing group that is part of the continuum-type specification, highlight the group label in the Entity list (see below) and click Edit.
When you click Edit to create or modify a group, GAMBIT opens either the Create Group or Modify Group forms, respectively. For instructions concerning the use of the Create Group or Modify Group forms, see "Using the Create Group Form" or "Using the Modify Group Form," respectively, in Chapter 2 of this guide.
Group
Volume
Face
Edge
specifies the particular entity (or entities) to which the continuum attribute is assigned.
Label | Type lists the labels (Label) and types (Type) of all topological entities currently associated with the current continuum-type specification.
Remove deletes the currently highlighted entity from the list of entities associated with the continuum-type specification.
Edit opens an Edit Lower Topology form, which allows you to specify whether or not lower geometry and/or geometry connected to the currently highlighted entity is included in the continuum-type specification. For instructions in the use of the Edit Lower Topology forms, see "Using Edit Lower Topology Forms" in Chapter 2 of this guide.


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