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cfcombine may be used to combine structured zones in a common grid (.cgd) or common flow (.cfl) file into a single zone. The zones being combined must have abutting faces with contiguous grid points, or (for .cfl files) be overlapping in a manner consistent with the NOLAP option in the cfsplit utility.

Input to cfcombine is specified in a keyword input file, with the three-letter extension .inp. Lines in the input file starting with a "/" are comments. The following keywords and parameters may be specified.

    CHECK   Checks the input file for errors without performing any operations.

FILE file_in The input .cgd or .cfl file, containing zones to be combined.

OUTPUT file_out The output common file, with the combined zones.

NOLAP nplanes The number of planes by which the split boundaries are overlapped. The overlapping must be in a manner consistent with the NOLAP specification in the cfsplit utility. However, in cfcombine NOLAP applies to all zones. Common flow files split with cfsplit can only be recombined if the same NOLAP value was used for all zones in cfsplit. This keyword may only be used with common flow (.cfl) files.

HALFCELL Indicates that the common boundary between the two zones being combined lies halfway between the adjacent grid surfaces, consistent with the HALFCELL specification in the cfsplit utility. When the two zones are combined, the common grid surface between the original two zones is removed. This option overrides any NOLAP specification. This keyword may only be used with common flow (.cfl) files.

COMBINE ZONE nzone1 face1 TO ZONE nzone2 face2
The COMBINE keyword tells cfcombine what zone and face to combine to what other zone and face. The parameters nzone1 and nzone2 are the numbers of the zones to be combined. The parameters face1 and face2 specify the adjoining faces of the zones to be combined. The adjoining faces must be specified in the form IMAX (or JMAX or KMAX) to I1 (or J1 or K1), and in that order, with I faces connecting to I faces, etc. When multiple zones are being combined into a single zone, only a minimal connection set is required.


Suppose we have the three-zone grid shown in the following figure.

Three-zone grid

Input three-zone grid for cfcombine

A two-zone grid may be created by combining zones 1 and 2 using the following input file for cfcombine, named cfcombine12.inp.

   / Input grid file
   FILE testa.cgd
   / Output grid file
   OUTPUT testb.cgd
   / Combine zones 1 and 2
   COMBINE ZONE 1 imax TO ZONE 2 i1

The terminal session is shown below. Lines in a slanted font are typed by the user.

   % cfcombine
             Select the desired version from the following list.
   0) END
   1) cfcombine
   Single program automatically selected.
   Omit the .inp extension!
   Enter cfcombine INPUT FILE ............. (<CR>=cfcombine.inp) : cfcombine12
    cfcombine - Version 1.11 (last changed 2007/02/13 23:23:07)
    * Warning: This software contains technical data whose export is           *
    * restricted by the Arms Export Control Act (Title 22, U.S.C., Sec 2751,   *
    * et seq.) or Executive Order 12470. Violation of these export-control     *
    * laws is subject to severe criminal penalties. Dissemination of this      *
    * software is controlled under DoD Directive 5230.25 and AFI 61-204.       *
    COMBINING ZONES FOR NEW ZONE   1 SIZE= ( 17, 11,  1)
    COMBINING ZONES FOR NEW ZONE   2 SIZE= ( 17, 11,  1)

The resulting grid is shown below.

Two-zone combined grid

Output two-zone grid from cfcombine

To create a single-zone grid from the original three-zone grid, the following two COMBINE commands would be used in the input file, instead of the single COMBINE command shown above.

   COMBINE ZONE 1 imax TO ZONE 2 i1
   COMBINE ZONE 2 imax TO ZONE 3 i1

Last updated 26 Aug 2015