CFD Utilities Files

!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
!
   program compress2d
!
!  Description:
!
!     Use of the original upstream volume grid compression capability still
!     provided here is now deprecated except perhaps for minimal compression.
!     Recommended is the most-recently added simplest-possible splitting option.
!     (The concern is over the possible effect of the compression on the nicety
!     of the original hyperbolic volume gridding.)
!
!     A retrofitted output (a plottable measure of skewness of the radial lines
!     of the input single-block grid) may suggest adjusting the forebody portion
!     of the underlying generatrix.  See further details below.
!
!     The original description of the deprecated compression follows:
!
!     This specialized program adjusts the single-block hyperbolic 2D volume
!     grid associated with a generatrix from CAPSULE_GRID by compressing its
!     forward portion to improve (?) initial flow calculations.  It prompts for
!     a handful of controls.  A heuristic new forward boundary is established as
!     a 2-space local parametric cubic spline (x and y vs. arc length) and the
!     input radial grid lines are intersected with it then redistributed.  The
!     otherwise untouched radial lines are also redistributed to ensure smooth
!     blending of the radial spacings.
!
!     The number of points in the radial direction for the output grid can
!     be changed along with the wall spacings (maybe constant) and outermost
!     spacings, or by preserving the relative spacings.  However, no such
!     radial redistribution is provided if the simple splitting option that is
!     now recommended is selected.  (Hypgen controls should be enough.)
!
!  Input Grid Format (from Gridgen/Hypgen-based script, with z = 0 everywhere;
!                     may be unformatted; single block):
!
!         285      101        1
!     0.00000000000e+00  8.96179650000e-06  3.59308720000e-05  8.08756720000e-05
!     1.43791190000e-04  2.24670450000e-04  3.23504450000e-04  4.40282210000e-04
!      :                  :                  :                  :
!
!     The input grid is assumed to have i along the surface and j in the radial
!     direction, and z = 0 everywhere.
!
!  Option to Derive a 3D Volume Grid From the Compressed 2D Grid:
!
!     "Umbrella" (faceted and open at the back) full-body surface grids have
!     been found difficult to grow hyperbolic volume grids from in Gridgen.
!     Therefore, an option is provided to read a spoked form of the faceted
!     surface grid and morph the plane 2D hyperbolic grid to each azimuthal
!     station of the spoked surface.
!
!     The expected surfaces are spoked_surface_fore.g and spoked_surface_aft.g
!     from CAPSULE_GRID.  The option is invoked automatically if the first of
!     these is found in the working directory, but a prompt allows skipping this
!     volume gridding if the 2D compression controls still need to be checked
!     graphically, if the surface is axisymmetric, or if there is no aft body.
!
!  Output Function File Containing a Measure of Radial Grid Line Skewness:
!
!     Experience shows that the DPLR alignment process can produce indentations
!     in the outer boundary (and corresponding surface heat flux irregularities)
!     if the radial grid lines, which are normal very close to the surface by
!     construction in the hyperbolic growth off the surface, deviate too much
!     from orthogonality further out from the [fore]body.  This is because the
!     skewed radial lines are longer than they would be if they weren't skewed,
!     so their arc lengths (and arc length changes for the same reason) become
!     shortened by the smoothing process more than they would be otherwise.
!     The surface point distribution in the [forebody] generatrix is the only
!     way to affect such skewing--through trial and error.  Spreading shoulder
!     clustering well forward along a conical flank, possibly with more points,
!     can reduce the indicated skewing.  The function file output here,
!     skewness.f[u], provides a graphical means of seeing whether a modified
!     generatrix has reduced the skewing or not.
!
!     The measure output at each grid point (i,j) is the angle in degrees
!     between the surface normal at (i,1) and the cell side defined by points
!     (i,j) and (i,j+1).  At j = nj, the nj - 1 result is copied.  This is
!     expected to be meaningful for forebodies only, where grid alignment
!     with the bow shock is so crucial to good surface heating predictions.
!
!     In view of the realization that compressing the upstream part of the
!     volume grid may do more harm than good, a simple option is now provided
!     (for BC purposes) to split the single block at an indicated i index
!     without any redistribution options.  Hypgen itself can produce the
!     desired radial point count and wall spacing.
!
!  History:
!
!     01/23/12  D.A.Saunders  Initial implementation, for fore+aft body cases.
!     01/24/12    "     "     Split the output grid into 2 blocks so that one
!                             can have free stream inflow BC at jmax and the
!                             other can have supersonic outflow BC.
!     03/16/12    "     "     Compressing forebody or forebody-like sting cases
!                             where the blending aft of the body is exactly at
!                             the aft end of the outer boundary needs control
!                             over the slope of the revised boundary there, and
!                             it doesn't need the splitting into two blocks.
!     08/28/12    "     "     For non-axisymmetric "umbrella"-type (faceted)
!                             geometries, use WARPQ3D morphing to produce a
!                             (compressed) 3D volume grid as well as the 2D one
!                             corresponding to the underlying generatrix.
!     08/29/12    "     "     Dinesh noted that the forebody diameter is a
!                             more natural reference length than body length
!                             (~6 diameters from the nose for the downstream
!                             boundary that the hyperbolic gridding should reach
!                             and multiple of the diameter for the desired up-
!                             stream boundary, depending on Mach and Alpha).
!     09/04/12    "     "     I forgot about WARPQ3D2, which has fewer arguments
!                             because work-space is allocated locally.
!     09/05/12    "     "     A prompt now allows suppression of the output 3D
!                             volume grid, either because the surface is axi-
!                             symmetric, or no aft body is present, or the 2D
!                             compression controls still need to be iterated on.
!     09/07/12    "     "     A SIAD (inflatable) case with a sharp vertex in
!                             the forebody generatrix prompted an option to
!                             redistribute the radial lines with the same
!                             relative spacing as in the uncompressed input
!                             2D volume grid.  Lines that have been compressed
!                             conflict with the assumptions of ADJUSTN, but an
!                             initial shuffle works around this as best we can.
!     09/13/12    "     "     The same relative spacing isn't much help for
!                             sharp vertices unless compression is limited.
!                             Preserving the existing wall spacing proves even
!                             worse, but it's now an option.  Rounding sharp
!                             corners is preferable if they're not critical.
!     11/13/14    "     "     The test for forebody or not needed a tolerance.
!     04/19/16    "     "     The test for forebody or not was using x when it
!                             should use y!
!     04/14/21    "     "     Went to add same-relative-spacing option, but it
!                             was already there.  Fixed one typo.
!     01/24/24    "     "     Added output of a volume file containing a measure
!                             of the skewness of the radial grid lines.
!     01/26/24    "     "     Arranged to skip the compression step, but always
!                             write skewness.f or skewness.fu depending on the
!                             input grid formatting.
!     05/22/26    "     "     Introduced a simplest possible splitting option
!                             at an indicated i index, with no radial redistri-
!                             bution (now the recommended choice as long as the
!                             Hypgen controls are appropriate).
!
!  Author:  David Saunders, ERC, Inc. at NASA Ames Research Center, CA
!                Later with AMA, Inc. at NASA ARC.
!
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