SBLOCK Version 0.2i

Authors: William M. Chan

Date: October, 1997.

SBLOCK stands for `Surface Blocking' and is a program for performing partial surface domain decomposition and surface grid generation for overset grids. The surface geometry will be covered by a set of overlapping seam grids and block grids. Seam grids are grids that are bounded by one or more control curves of the surface. The control curves can be intersection curves, curves alone surface discontinuities, curves alone a high curvature contour of the surface, etc. Block grids are grids on the surface regions not covered by the seam grids. The seam grids can typically be generated using the SURGRD overset surface grid generator. Given a surface geometry definition in the form of multiple panel networks, and a set of seam grids, SBLOCK can be used to automatically generate the block grids.

Limitations

Input/output files

1. Input parameters file (see below for explanation of parameters).
2. Reference surface grid file *.
3. Seam surface grid file *.

* PLOT3D multiple unformatted surface grid format. Filenames are specified in input parameters file.

A number of output files are produced by SBLOCK. These include intermediate/final grid files and PLOT3D command files for viewing the grid files.

   mgrid.dat  - marker cells
   bcell.dat  - block cells
   bgrid.dat  - block patches
   bsgrid.dat - block grids after stitching block patches
   brgrid.dat - block grids after spacing adaption to seam grids

   .dat - extrapolated block grids (after extrapolation to
                    provide overlap).  is specified in the
                    input parametes file.

Input parameters

Seam surface grids filename

Basename of file for output block grids. The extensions '.dat' and '.com' are added to the grid and PLOT3D command files, e.g., if the basename is block, then the output grid and command filenames are block.dat and block.com, respectively. Please avoid using conflicting names to those used by the code, i.e. do NOT use mgrid, bcell, bgrid, bsgrid for the basename.

     NRFAM  = 0   - assume reference surface is defined by all L=1 surfaces
                    in input reference surface file.
            > 0   - specify subsets of grids from reference surface file
                    to define reference surface (only 1 family can be used
                    currently)

     Enter the following block if NRFAM > 0
     {
      NRSUB = number of subsets
      For n=1,nrsub, enter
        {
         NG    = grid number of subset
         JS,JE,KS,KE,LS,LE = j,k,l start, end indices of subset
         IFAM  = family number (not used currently)
        }
     }

     ICOA   = coalescence parameter in K
     DSM    = maximum grid spacing of marker cells
     DSB    = maximum grid spacing in block grids

     NSMOO  = number of elliptic smoothing step per cycle.
     IBSP   = 0  do not adapt block grid boundary spacing to neighboring seam grids
            = 1  adapt block grid boundary spacing to average min. seam grid spacing
            = 2  adapt block grid boundary spacing to average diag. seam grid spacing

     TOLB   = max gap size between patches on reference surface.
     NPSMAL - block patches with NPSMAL points or less in either J or K
              direction will be considered for Type-2 stitching.
     ISTCH  =  0  - perform both Type-1 and Type-2 stitching
            =  1  - perform Type-1 stitching only
            =  2  - perform Type-2 stitching only

     IEXT   =  0  - no extrapolation after stitching
            = -1  - extrapolate but do not project
            =  1  - extrapolate and project
     SRMAX  = max stretching ratio allowed in block grids (this will affect
              the total number of points used)

Output PLOT3D command files

     refs.com  - reference surface (input)
     sgrid.com - seam surface grids (input)
     mgrid.com - marker cells
     bcell.com - block cells
     bgrid.com - block surface patches (output)
     bsgrid.com - unextrapolated stitched block surface grids (output)
     brgrid.com - unextrapolated stitched block surface grids with
                  adapted spacing (output)
     .com - extrapolated stitched block surface grids (output)

Program parameters in main program

     MSUB  = max number of surface subset
     MGRID = max (number of grids in input reference grids file,
                  number of grids in input seam surface grids file)
     MQG   = max number of block grids
     NGLIM = max number of grids allowed in a PLOT3D grid file

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