Typically, there is one zone section for each zone referenced by the grid. Although some grid zones may not have corresponding sections, there cannot be more than one zone section for each zone.

The zone section has the following form:

(39 (zone-id zone-type zone-name domain-id)(
(condition1 . value1)
(condition2 . value2)
(condition3 . value3)
 .
 .
 .
  )) 

Grid generators and preprocessors need only provide the section header and leave the list of conditions empty, as in:

(39 (zone-id zone-type zone-name domain-id)())

The empty parentheses at the end are required. The solver adds conditions as appropriate, depending on the zone type.

When only zone-id, zone-type, zone-name, and domain-id are specified, the index 45 may be used for a zone section. However, the index 39 must be used if boundary conditions are present, because any and all remaining information in a section of index 45 after zone-id, zone-type, zone-name, and domain-id will be ignored.

In meshing mode, the zone name and type can be extracted from the boundary condition section 39 (refer to the Fluent User’s Guide for details) or 45, but only section 39 can be written.

The zone-id is in decimal format. This is in contrast to the use of hexadecimal in the grid sections.

The zone-type is one of the following:

degassing
exhaust-fan
fan
fluid
geometry
inlet-vent
intake-fan
interface
interior
internal
mass-flow-inlet
outflow
outlet-vent
parent-face
porous-jump
pressure-far-field
pressure-inlet
pressure-outlet
radiator
solid
symmetry
velocity-inlet
wall
wrapper 

The interior, fan, porous-jump, and radiator types can be assigned only to zones of faces inside the domain. The interior type is used for the faces within a cell zone; the others are for interior faces that form infinitely thin surfaces within the domain. Fluent allows the wall type to be assigned to face zones both on the inside and on the boundaries of the domain.

Some zone types are valid only for certain types of grid components (for example, cell zones can be assigned only either fluid or solid type). All other types listed can be used for only boundary (face) zones.

The zone-name is a label for the zone. It must be a valid Scheme symbol and is written without quotes. The rules for a valid zone-name are as follows:

Some examples of zone sections produced in the meshing mode are as follows:

(39 (1 fluid fuel 1)())
(39 (8 pressure-inlet pressure-inlet-8 2)())
(39 (2 wall wing-skin 3)())
(39 (3 symmetry mid-plane 1)())