Zone Type Assignment

This section describes zone naming and the zone type assignment process.

Zone Naming

By default, zones are named after the part and body from which they are derived. For example, part "part" and body "solid body" will result in a zone name of "part-solid_body." When the zone name is created:

  • Any invalid characters (such as the space in "solid body") are replaced by an underscore character ("solid_body").

  • Names that begin with a digit are prefixed by "zone."

  • If the part name and the body name are identical, only the body name is used to create the zone name. The same rule applies to single body parts.

Note:  If you set the Auto Zone Type Assignment option to Off (as described in Meshing Options on the Options Dialog Box), all boundary zones are set to the default zone type WALL.

If a boundary zone was created for a Named Selection (as described in Classes of Zone Types in Ansys Fluent), the name of the boundary zone is set to the name of the Named Selection.

In cases where the zone naming process could lead to conflicting zone names (for example, in a situation where the potential exists for a zone name that is already in use to be used to name a new zone), one of the following approaches is used:

  • If the zone type is not similar to the zone name in question, the zone type will be prefixed to the zone name to make it unique. For example, an existing continuum zone named "fluid" and a new boundary zone named "fluid" (with zone type WALL) will result in the boundary zone being renamed "wall-fluid."

    A unique integer will be suffixed to the zone name, preceded by a dot character (.). For example, an existing continuum zone named "solid" (with zone type SOLID) and another continuum zone named "solid" (with zone type FLUID) will result in the continuum zone being renamed "solid.1."

  • If the zone type is similar to the zone name in question, the approach is dependent on whether the zone is a continuum zone or a boundary zone:

    • If multiple continuum zones have the same type and same zone name, they are merged into a single continuum zone.

    • If multiple boundary zones have the same type and same zone name, a unique integer will be suffixed to the zone name, preceded by a dot character (.). For example, an existing boundary zone named "wall" and a second boundary zone named "wall" will result in the second boundary zone being renamed "wall.1." Subsequent boundary zones named "wall" will be renamed "wall.2," "wall.3," and so on.

Because part and body names influence the creation of continuum zones in Ansys Fluent, it is best practice to assign distinct part and body names that follow these rules:

  • Names should include only allowable characters. Allowable characters include all alphanumeric characters as well as the following special characters:

    ` ! $ % ^ & * _ + - = : < > . ? /

    All other characters, including spaces, are invalid. If an invalid character is used, it is replaced by an underscore (_) upon export.

  • It is not sufficient for part and body names to differ by case only. This approach may lead to name conflicts for zones in Ansys Fluent, because names are converted to all lowercase characters upon export.

  • Using "INTER" as zone name or part of a zone name should be avoided. Because the mesher does not allow named selections with identical names and interface definitions require two named selections, using "INTER" can cause zone type conflicts. 

Zone Type Assignment Process

The section is applicable to boundary zones only.

The zone type is derived from the zone name. To assign zone types, the string comparison operations detailed below are performed during the export process. These string comparison operations, which correspond to the naming conventions described in Standard Naming Conventions for Naming Named Selections, are applied in the order in which they are listed below (that is, at first an exact match is tested, after that a partial match is tested, etc.) and are always case-insensitive. For example, fan, Fan, FAn, and faN are all exact matches for the 'FAN' string comparison and result in a zone type of FAN being assigned.

When the search operation begins, it will start by searching the first portion (or sub-string) of the string and if no match is found, it will search for a match anywhere in the string. For example, if a Named Selection with the name wall_inlet_flange is defined, it will be exported as zone type WALL. The 'inlet' portion of the name will have no effect on zone type assignment.

In some cases a name may match multiple patterns or rules, and the expected zone type may not be assigned. For this reason it is strongly advisable to use only unambiguous names that exactly match one of the rules presented below.

Once they are exported, names are all lowercase. The single quotation marks that are shown enclosing the strings below are not considered during the string comparison operations.

  1. Exact matches are checked:

    'AXIS'
'EXHAUST_FAN'
'FAN'
'INLET_VENT'
'INTAKE_FAN'
'INTERFACE'
'INTERIOR'
'INTERNAL'
'MASS_FLOW_INLET'
'OUTFLOW'
'OUTLET_VENT'
'POROUS_JUMP'
'PRESSURE_FAR_FIELD'
'PRESSURE_INLET'
'PRESSURE_OUTLET'
'RADIATOR'
'RECIRCULATION_INLET'
'RECIRCULATION_OUTLET'
'SYMMETRY'
'THIN'
'VELOCITY_INLET'
'WALL'

  2. Partial matches are considered only if an exact match was not found in step 1:

    'AXIS'
{'EXHAUST' && 'FAN'}
'FAN'
{'INLET' && 'VENT'}
{'INTAKE' && 'FAN'}
'INTERFACE'
'INTERIOR'
'INTERNAL'
{'MASS' && 'FLOW' && 'INLET'}
'OUTFLOW'
{'OUTLET' && 'VENT'}
{'POROUS' && 'JUMP'}
{'PRESSURE' && 'FAR' && 'FIELD'}
{'PRESSURE' && 'INLET'}
{'PRESSURE' && 'OUTLET'}
'RADIATOR'
{'RECIRCULATION' && 'INLET'}
{'RECIRCULATION' && 'OUTLET'}
'SYMMETRY'
{'VELOCITY' && 'INLET'}

  3. String comparisons to the special abbreviations listed in the table below are performed if no match was found in step 1 or step 2. If an exact match to one of the strings listed in the table is found, the corresponding zone type is assigned:

    When a match for this string is found...This zone type is assigned...
    'CNDBY'
    		INTERFACE
    'EXFAN'
    		EXHAUST FAN
    'IFACE'
    		INTERFACE
    'IN'
    		PRESSURE INLET
    'INFAN'
    		INTAKE FAN
    'INTERFACE'
    		INTERFACE
    'IVENT'
    		INLET VENT
    'MASFI'
    		MASS FLOW INLET
    'OUT'
    		PRESSURE OUTLET
    'OVENT'
    		OUTLET VENT
    'PFAR'
    		PRESSURE FAR FIELD
    'PORJ'
    		POROUS JUMP
    'PRESF'
    		PRESSURE FAR FIELD
    'PRESI'
    		PRESSURE INLET
    'PRESO'
    		PRESSURE OUTLET
    'PRESS'
    		PRESSURE FAR FIELD
    'RAD'
    		RADIATOR
    'RINLT'
    		RECIRCULATION INLET
    'ROUT'
    		RECIRCULATION OUTLET
    'SLIDE'
    		INTERFACE
    'SYM'
    		SYMMETRY
    'SYMET'
    		SYMMETRY
    'SYMM'
    		SYMMETRY
    'VELF'
    		VELOCITY INLET
    'VELI'
    		VELOCITY INLET

  4. Partial matches are considered if no match was found in steps 1, 2, or 3. If a partial match to one of the strings listed in the following table is found, the corresponding zone type is assigned:

    When a match for this string is found...This zone type is assigned...
    'EXHAUST'
    		EXHAUST FAN
    'INLET'
    		VELOCITY INLET
    'OUTLET'
    		PRESSURE OUTLET
    'SYM'
    		SYMMETRY
    'THIN'
    		THIN
    'WALL'
    		WALL

  5. If none of the string comparisons described in steps 1, 2, 3, or 4 result in a match, the boundary zone is assigned zone type WALL by default.

Note:
Handling Periodic Regions

To export matching face meshes as PERIODIC boundary zone types, you must perform the following steps:

  1. Define matching face meshes (for 3D) or edge meshes (for 2D only) as Periodic Regions or Cyclic Regions in a Symmetry folder or as Match Controls or Arbitrary Match Controls.

  2. Define two Named Selections for each periodic boundary condition, one Named Selection per side, ensuring that ”periodic” is used in the name (for example, periodic1A, periodic1B...). The same Named Selections could be used to define the periodic or cyclic region.

Note:

  • Periodic regions must belong to the same Fluent mesh cell zone to ensure a successful export.

  • When match controls on faces are used, only one periodic or cyclic transformation is supported (for example, you can export multiple match controls as long as they use the same coordinate system and have the same angle/translation).

Special Cases

Be aware of the following special cases related to boundary zone type assignment:

  • If Physics Preference is set to CFD and no other zone assignment has been explicitly defined, all zones are exported as FLUID zones. See Fluent Mesh Export for more information.

  • A boundary zone type of INTERFACE is assigned automatically to the contact source and contact target entities that compose contact regions at the time of mesh export. For this reason, you are not required to explicitly define INTERFACE zones to resolve contact regions. The zone type of INTERFACE, along with the contact information, is written to the mesh file.

    When reading the mesh file, Ansys Fluent creates a mesh interface for each contact region automatically. Each interface can consist of any number of INTERFACE zones for the source and any number of INTERFACE zones for the target.

    For 3D meshes, only face zones referenced in the contact region are considered during export. For 2D meshes, only face zones consisting of edges are considered. Each contact region can contain one or more face zones as sources and one or more face zones as targets. If any entity referenced in a contact region (either as source or target) is also contained in a Named Selection, that contact region is not considered during export.

    For more accurate results in cases in which one face zone in a pair has a higher element count than the other, the zone with the lower element count should be defined as Interface Zone 1 of the mesh interface and the zone with the higher element count should be defined as Interface Zone 2. In the transfer of the contact region source and target regions it is ensured that the source regions are defined as interface zone 1 and the target regions as interface zone 2.

  • A boundary zone type of INTERNAL is assigned automatically between two FLUID zones (sharing a common boundary) at the time of mesh export. For this reason, you are not required to explicitly define an INTERNAL zone in such cases if the name of this zone does not contain any special name derived from the part/body or Named Selection name.

  • A boundary zone type of WALL is assigned automatically to a baffle, unless the baffle is part of a Named Selection that was defined in the Ansys DesignModeler application or the Meshing application, and the name of the Named Selection results in a different zone type assignment.

  • A boundary zone type of WALL is assigned automatically between a FLUID zone and a SOLID zone at the time of mesh export. For this reason, you are not required to explicitly define a WALL zone in such cases. When reading the mesh file, Ansys Fluent will generate an additional WALL SHADOW zone automatically.