CFD Utilities Files

CAPSULE_GRID performs automated discretization of analytically-defined
generatrices for typical (and not-so-typical) axisymmetric capsules such
as 70-degree sphere/cones with optional aft bodies.  For zero angle of
attack cases, related procedures produce the associated initial volume
grid needed for flow field calculations.  Non-analytic input generatrices
are also handled.  For angle of attack cases, a surface grid is also
produced, with the singular point region at the nose (and aft body if
present) replaced by morphed quadrant patches.  Volume grids may likewise
be produced with related procedures.

Please see Capsule_Grid.pdf and the header of capsule_grid.f90 for further
details.

06/30/2016    "    "      A new option in CURVDIS to work with adjusted
                          curvatures that are artificially broadened onto
                          flat/low-curvature segments appears to be good
                          for analytic geometries but unreliable for input
                          generatrices of unknown quality/precision.
                          New controls flat_blend_fore & flat_blend_aft
                          allow this option to be suppressed.  It was
                          prompted by a clear need to resolve heat flux
                          spikes at the shoulder better by spreading the
                          tight shoulder grid spacing forward onto the
                          conical flank.  This should work for Apollo-
                          type spherical sections too (large radius/low
                          curvature) given that we work with normalized
                          geometry during curvature-based redistribution.
                          Namelist controls are now printed to standard
                          output.
10/27/2016    "    "      Aft-end stretching towards the symmetry axis in
                          the generatrix is undesirable.  3D surfaces
                          replace this region with uniform quadrants.
                          Therefore, do similar to the generatrix, using
                          ni_regrid_aft_body and a heuristic number of
                          uniform points at the end.
04/05/2018    "    "      An indexing error was found in the above uniform
                          redistribution of the aft generatrix end.
08/23/2018    "    "      The analytic aft body case's forcing of uniform
                          spacing away from the aft stag. point was not
                          right because x/rgen(:) was being reused for the
                          aft body (starting from 1, not numi_forebody).
09/25/2019    "    "      Rerunning on the capsule-on-a-sting analytic
                          case gave troubling aft-body results, traced to
                          interference of the vertex-detection scheme in
                          CURVDIS with the (later) scheme for broadening
                          the curvature-based shape function on to flat or
                          low-curvature segments. Better blending on to
                          such segments (and either side of sharp corners)
                          is highly desirable, but fraught with potential
                          difficulties due to the unavoidable heuristics.
10/30/2019    "    "      Introduced nblend_fore_aft control. The default
                          of 8 can mean poor results going from tight
                          spacing on the shoulder to larger spacing on
                          the aft cone. Spreading the blending over more
                          points should help.
11/30/2019    "    "      A pitot tube case from Dinesh revealed that an
                          input generatrix did not have the scale factor
                          applied as for analytic cases. Rectified now.
01/17/2020    "    "      Minor tweaks to the "umbrella" case for it to
                          work in the absence of a rounded shoulder aft
                          of the underlying cone and a nose cap larger
                          than that cone.
06/17/2021 -  "    "      Parachute cones with different TPS material have
06/25/2021                required splitting of aft body surface patches
                          for BC purposes (catalycity).  The dimensions
                          either side of the split need to be of the form
                          4n + 1 in order for the initial fine grid to be
                          coarsened once for production use (221) and
                          coarsened again for grid sequencing (441|442)
                          during an initial unaligned grid solution.
                          Introduced x_parachute_cone control. Patch
                          dimensions either side of this x > 0. will be
                          adjusted to the closest 4n+1 form as well.
                          The number of surface patches becomes 16.
09/07/2021 -  "    "      New asymmetric and lower_generatrix inputs
09/29/2021                enable handling of an asymmetric forebody with
                          an optional axisymmetric aft body, as prompted
                          by Mars Sample Return Lander configuration V21.
10/29/2022    "    "      The parachute cone split option, which forces
                          point counts either side to be 4n + 1, means
                          there is likely to be redistribution (splining)
                          across the PC lid corner.  Now we look for such
                          a corner and preserve it exactly.  The same may
                          be needed upstream of the split, although the
                          shoulder step corner of SRL DAC-2.2 seems to be
                          unaffected.
05/24/2023                The 10/29/22 extension to preserve a parachute
                          lid corner during redistribution associated with
                          capturing x_parachute_cone was thwarted by a
                          corner at a shoulder step combined with a less
                          sharp PC lid corner (SRL Rev B having a rounded
                          lid).  This idea has been abandoned.  If the
                          capturing of x_parachute_cone loses geometry
                          features, the only work-around is to provide a
                          generatrix with the desired points and point
                          counts, and to ensure the generatrix is retained
                          through proper choice of numi_forebody and
                          nu i_aft_body.  (Sorry.)