CFD Utilities Files

Description:

   COMBINE_BLOCKS appends the blocks of a second grid to those of an
initial grid in PLOT3D format.  Accompanying flow solutions are optional.
In particular, it has proved handy for appending tile cavity blocks to
smooth OML grids during damage/repair studies for the Shuttle program.

   Some specialization is pragmatic for cavity cases when solution files
are present.  Wing leading edge plug repair cases are also handled by this
same option, except that a second specialized procedure (PLUG_INTERP)
should then be used to adjust the outer boundary flow interpolations.

   The input and output files are prompted for.  If a flow solution is
present with the first grid but not the second, then blocks corresponding
to the second grid file (presumably in a cavity) are added to the output
solution file and their flow fields are initialized from the k = 1 layer
of the flow for the first set of blocks as follows:

       pressure is reduced by a factor of 10 (default; now prompted for);
       velocity components are zeroed;
       remaining state variables are retained.

   The nearest point in the first grid's k = 1 surface layer is located
efficiently (for each volume point of the cavity blocks) via an ADT search.
This avoids dealing with interface files and produces smoothly varying flow
within the cavity blocks which is presumably a little better than choosing
some constant flow throughout each cavity block.

Further clarification of flow-solution cases:

   (1) If both grids are accompanied by solution files, the solutions may
       be either vertex-centered or cell-centered - it doesn't matter.
       The operation is quite general - just the number of flow variables
       must be the same in each solution file.

   (2) If no solution file accompanies the second grid, then the first
       grid and solution should both be cell-centered as output by the
       POSTFLOW procedure for DPLR solutions.  The second grid, on the
       other hand, is most conveniently vertex-centered.  In this case,
       it is converted here to cell-centered form (with halos) prior to
       transcribing to the output grid, and a corresponding flow solution
       is generated as described above.