CFD Utilities Files

NOTE:  GSMOOTH's option to check cell volumes has been its only use at
       Ames in recent years.  Nevertheless, as a driver for ELLIP3D, it
       may prove helpful to somebody some day.

   GSMOOTH applies the elliptic grid smoothing utility, ELLIP3D, to the
specified block of a multiblock grid file (or to a single-block grid).
The smoothing is CPU-intensive enough that treating more than one block
can reasonably be expected to be done with separate runs.  The standard
PLOT3D formats are supported (formatted or unformatted, with or without
IBLANK).  (Actually, translation from the CFD_IO_PACKAGE to the XYZQ_IO
package has lost the IBLANK option, though it could easily be restored
if the need arises since XYZQ_IO has iblank analogues.)

   This version can be used to check cell volumes of the target block
(and nothing else except perhaps extract the block) by using ITMAX = 0.
ITMAX = -1 checks the cell volumes for ALL blocks (and nothing else).

   Only Euler-type grid blocks are likely to be smoothed successfully--
Navier-Stokes-type blocks should be derived from smoothed Euler blocks.

Sample Control File (gsmooth.inp):

   ITMAX OMEGA CONV   EXPI1/I2/J1/J2/K1/K2    BGPHI  BGPSI  BGOMG  FGMODE
    100   1.3  4.0  .45 .45 .45 .45 .45 .45  'YYYY' 'YYYY' 'YYYY' 'YYYYYY'
   PRINT FGLIM URFG
      F   1.0  0.1

Control Descriptions:

   (Here, "foreground" refers to control of orthogonality at a boundary;
    "background" refers to control of interior spacing from a boundary.)

   ITMAX     Number of smoothing iterations:
             0 means just check cell volumes for the target block (and
               maybe extract the block);
            -1 means check the cell volumes of ALL blocks (& nothing else)
   OMEGA     Over-relaxation factor for SLOR smoothing iterations
   CONV      Number of orders of magnitude reduction in max. dX, dY, or dZ
   EXPI1     Exponential decay factors for the foreground terms at the
   EXPI2     6 faces
   EXPJ1
   EXPK1
   EXPK2
   BGPHI     'YYYY' turns on background control of interior spacing from
             the I faces (Phi effects) at edges J1, J2, K1, K2 resp.
   BGPSI     'YYYY' turns on background control of interior spacing from
             the J faces (Psi effects) at edges I1, I2, K1, K2 resp.
   BGOMG     'YYYY' turns on background control of interior spacing from
             the K faces (Omega effects) at edges I1, I2, J1, J2, resp.
   FGMODE    'NNNNNN' turns off foreground effects at all 6 faces;
             'YYYYYY' turns on index-based orthogonality control;
             any mixture of controls is permitted (e.g., 'NYYYNN')

   PRINT     T displays 3-D smoothing iterations in gsmooth.out
   FGLIM     Growth limiter for foreground terms
   URFG      Under-relaxation factors for changes in foreground terms

History:

   06/30/99  D.A.Saunders  Initial implementation.
   07/03/99    "      "    ELLIP3D's writes to unit 6 must come to the
                           screen, so forget about a printable output file.
   02/22/00    "      "    Suppress the full-size output file if the number
                           of smoothing iterations is 0.  The optional copy
                           of the target block remains an option.  Also,
                           check ALL block cell volumes if ITMAX = -1.
   02/10/14    "      "    Replaced CFD_IO_PACKAGE with xyzq_io package.
   03/12/22    "      "    Handy test program for verifying pyramid_volume
                           and hex_volume (alternatives to Antony Jameson's
                           approach in subroutine cellvol, intended for
                           unstructured grids).
   03/15/22    "      "    Test alternative tet_vol and hex_vol similarly.
   03/16/22    "      "    The 03/15/22 approach is preferable.  Retain it
                           as corroboration of the Jameson scheme.  Monitor
                           the volume summed over all blocks as a further
                           comparison.

Author:  David Saunders, ERC, Inc./NASA Ames Research Center, CA.