00_README.txt
-------------

Introduction:

Included in this directory is a small (1.7M hexahedron mesh) Cart3D
test case for the triceratops geometry.  The geometry is open source,
so there are no issues passing this to outside collaborators.

Cart3D is a high-fidelity flow analysis package for conceptual and
preliminary aerodynamic design.  Cart3D uses "Cartesian" meshes with
Adaptive Mesh Refinement (AMR).  The mesh is somewhat like a an
octree, but without a single root node.  This is sometimes referred to
as a "forest of octrees".  The data are "cell centered," i.e., the
data are per hexahedron.

For more on Cart3D:  https://www.nas.nasa.gov/software/cart3d.html


The Files:

Here is what we are including:

   cart3d_t-cera/
     ├── 00_README.txt    -- this file
     ├── mach.png         -- flow snapshot
     ├── Components.i.tri -- Cart3D surface triangulation file (ascii)
     ├── Mesh.c3d.Info    -- Cart3D Mesh Info file with meta data for mesh
     ├── Mesh.mg.c3d      -- Cart3D mesh file
     ├── check.01116      -- Cart3D checkpoint file with solution data
     ├── rho.bin          -- density, 1 float per hexahedron
     ├── u.bin            -- X component of velocity, 1 float per hexahedron
     ├── v.bin            -- Y component of velocity, 1 float per hexahedron
     ├── w.bin            -- Z component of velocity, 1 float per hexahedron
     ├── pressure.bin     -- pressure, 1 float per hexahedron
     ├── hexas.bin        -- hexahedra definitions, 4 ints per hexahedron
     ├── hexa_types.bin   -- hexahedra types, 1 byte per hexahedron
     ├── tec.dat          -- tecplot format volume mesh & solution,
     |                         finite-element (brick) ascii
     └── Components.i.plt -- surface triangulation with solution
                               that can be read into tecplot 

A bit more detail regarding the files:

hexas.bin:
This is a binary file, with 4 4-byte integers (little endian) per
cubic hexahedron.  The integers are in an array-of-structs layout:
4 consecutive integers specify a hexahedron.  The coordinates are in
integer.  The first three integers specify the low-corner of the
hexahedron, the fourth integer specifies the refinement level, r.  The
size of the hexahedron is based on the refinment level, 1 << r.  The
refinement levels range from 8 to 18.  Refinement level 8 would be the
finest, with hexahedra that have a side length of 256.

hexa-types.bin:
This is a binary file, 1 byte per hexahedron.  Full hexahedra (i.e.,
not intersected by model surfaces) are assigned type 1, cut hexahedra
are assigned 2, and split hexahedra are assigned 3.  A cut hexahedron
is intersected by the model surfaces and the remaining volume inside
the domain is a single connected component.  A split hexahedron is
intersected by the model surfaces and the result is more than one
subvolume remaining in the domain, i.e., multiple connected
components.  In the native Cart3D solution files included with this
dataset the solver writes data for each subvolume produced by split
hexahedra.  For the simplified output in hexas.bin and hexa_types.bin,
we arbitrarily choose 1 of the split hexahedron subvolumes to be
representative for the hexahedron so that the number of scalars in
rho.bin. u.bin, v.bin, w.bin and pressure.bin matches the number of
hexahedra.

rho.bin. u.bin, v.bin, w.bin and pressure.bin:
These are binary files, 1 little-endian float per hexahedron,
containing density, velocity components and pressure, respectively.


Basic Stats:

# r_min: 8
# r_max: 18
# integer bounding box: ((0, 0, 0), (1572865, 1572865, 1572865))
# real bounding box: ((-7.22795, -7.47708, 0), (7.72397, 7.47643, 15))
# i_to_r_scaling: (9.50617e-06, 9.50718e-06, 9.53674e-06)
# r_to_i_scaling: (105195, 105184, 104858)
# smallest_cell_size: (0.00243358, 0.00243384, 0.0024414)
# card(H) (i.e., the number of hexahedra): 1715932


Please contact us with any questions/issues.

Michael; micahel.aftosmis@nasa.gov
Patrick; patrick.moran@nasa.gov