CFD Utilities Files

CONES_OF_SIGHT Description:

   CONES_OF_SIGHT is an adaptation of LINES_OF_SIGHT, q.v.  It retains the
   functionality of its predecessor if the indicated cone angle is zero.
   At the time of writing, a third variation working with lines defined by
   points on a hemisphere is planned - see HEMISPHERES_OF SIGHT.

   Most of the following is carried over from LINES_OF_SIGHT.

Outline:

   For a list of surface pts. (grid indices or (x,y,z) coordinates) and the
   associated volume grid, generate lines of sight - i.e., straight lines
   normal to the surface and extending to the outer boundary with pt. dis-
   tributions close to those of the local radial grid lines.  The results
   are saved in PLOT3D multiblock form (one line of sight per block)
   compatible with the earlier FLOW_INTERP, which can perform the flow
   interpolations and tabulations that are normally what are really desired
   for application to hypersonic flows.

   (Later:) If a cone angle > 0 is specified, the output blocks contain the
   9 lines defined by the 9-pt. O(h^6) formula for integration on a circle
   of radius h on pp. 891-892 of Abramowitz and Stegun.  The lines are in
   clockwise order from the center out, so the corresponding quadrature
   coefficients are 1/6, 1/24, 1/24, 1/24, 1/24, 1/6, 1/6, 1/6, 1/6.

   This version can also read a structured surface grid for the target pts.
   to simplify using a thinned form of the relevant volume grid's surface.

Initial assumptions (probably generalizable, but they may not need to be):

   o  The structured volume grid contains one layer of blocks, with k = 1
      at the wall.  This simplifies determination of the inner and outer
      boundary patches.  (To overcome these restrictions, one could use the
      boundary condition data employed by the relevant flow solver.)

Strategy:

   o  Read the entire volume grid and extract the inner & outer boundaries
      as multiblock surface grids.

   o  For all points defining lines of sight, search the inner boundary and
      save the relevant patch number and cell indices.

   o  Build a new search tree from the outer boundary.

   o  For each inner surface point defining a line or lines of sight:

      > Construct a two-point line normal to the wall with length that of a
        local radial line.  This should be at least as long as the straight
        line distance to the outer boundary.

      > Intersect the line with the outer boundary and transform the point
        distribution of the radial line to the relevant line portion.

      > If the specified cone angle is not zero, derive 8 more lines of
        sight from the first and impose the same relative distributions.

Input surface point format (read to EOF):

   Either                                      or

   n   i   j                                   x   y   z
   n   i   j                                   x   y   z
   n   i   j                                   x   y   z
   :   :   :                                   :   :   :

   where n = block number and k = 1 is implied.

History:

   10/07/05  D.A.Saunders  Initial design of LINES_OF_SIGHT.
   11/14/05    "     "     Fixed a bug in allocating radial_lines(ib).
   11/22/05    "     "     Expanded the range of t for INTSEC6 to 2, not
                           1.1; added the option to read a structured
                           surface grid rather than a list of indices or
                           coordinates.
   03/06/06    "     "     Added the cone angle option.
   03/07/06    "     "     Renamed it as CONES_OF_SIGHT.

Author:  David Saunders, ELORET/NASA Ames Research Center, CA