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UNSTRUCTURED_EXPLICIT

Defines an unstructured grid through a list of cells and connectivity. Cells are defined by an id, coordinate and volume while connections are composed of two cell ids, an area and a face-center coordinate.

ASCII File Format

The first line specifies the number of cells, followed by one line per cell defining the cell ID, center coordinate and volume (in units of meters). The number of connections are then specified, followed by one line per connection defining the two cell ids on either side of the connection, the face center coordinate and the face area. Note that the center coordinates for Voronoi cells and faces are not necessarily the centroid.

CELLS <integer>: Number of cells in grid

CONNECTIONS <integer>: Number of connections in grid

CELLS #
1 X_coordinate Y_coordinate Z_coordinate VOLUME
...
# X_coordinate Y_coordinate Z_coordinate VOLUME
CONNECTIONS @
CELL_a CELL_b X_coordinate Y_coordinate Z_coordinate AREA
...
CELL_y CELL_z X_coordinate Y_coordinate Z_coordinate AREA

Example

Example explict unstructured grid (see mixed.uge)

CELLS 15
1 4.0625 4.0625 4.0625 5.20833
2 4.375 4.375 3.125 2.60417
3 3.3333 3.3333 3.75 7.8125
4 3.3333 1.6667 3.75 7.8125
5 3.3333 1.6667 1.25 7.8125
6 1.25 3.75 3.75 15.625
7 2.1875 4.0625 0.9375 1.30208
8 2.1875 3.4375 1.5625 1.30208
9 1.25 3.75 2.1875 2.60417
10 1.25 4.6875 1.25 2.60417
11 1.25 1.25 3.75 15.625
12 1.25 1.25 1.25 15.625
13 1.25 2.8125 1.25 2.60417
14 0.3125 3.75 1.25 2.60417
15 1.25 3.75 0.3125 2.60417
CONNECTIONS 24
1 2 4.16667 4.16667 3.3333 6.25
1 3 3.75 3.75 3.75 8.8388
3 4 3.75 2.5 3.75 6.25
3 6 2.5 3.75 3.75 6.25
4 5 3.3333 1.6667 2.5 3.125
4 11 2.5 1.25 3.75 6.25
5 12 2.5 1.25 1.25 6.25
6 9 1.25 3.75 2.5 6.25
6 11 1.25 2.5 3.75 6.25
7 8 2.08333 3.75 1.25 2.2097
7 10 2.08333 4.5833 1.25 2.2097
7 15 2.08333 3.75 0.41667 2.2097
8 9 2.08333 3.75 2.08333 2.2097
8 13 2.08333 2.91667 1.25 2.2097
9 10 1.25 4.48333 2.08333 2.2097
9 13 1.25 2.91667 2.08333 2.2097
9 14 0.41667 3.75 2.08333 2.2097
10 14 0.41667 4.48333 1.25 2.2097
10 15 1.25 4.48333 0.41667 2.2097
11 12 1.25 1.25 2.5 6.25
12 13 1.25 2.5 1.25 6.25
13 14 0.41667 2.91667 1.25 2.2097
13 15 1.25 2.91667 0.41667 2.2097
14 15 0.41667 3.75 0.41667 2.2097

HDF5 File Format

Two HDF5 datasets (Cells and Connections) are placed within a group named Domain within the HDF5 file. Cells group defines the cell center and the cell’s volume through two subgroud named Centers (a 2D group with center’s XYZ coordinates per cells) and Volumes. Then the Connections group defines the connection (i.e. face) properties by specifying the connection area with a Areas subgroup, the two cell ids on either side of the connection with a Cell ids 2D subgroup, and the connection centers with Centers 2D subgroup.

As an example, consider the ASCII example above with 15 cells and 24 connections.

Cells/Centers

Domain/Cells/Centers is a 2D float dataset sized 15x3 (number of cell x 3) [e.g. numpy.zeros((15,3),dtype=’f8’)] with data:

# X, Y, Z coordinate
4.0625 4.0625 4.0625
4.375 4.375 3.125
3.3333 3.3333 3.75
3.3333 1.6667 3.75
3.3333 1.6667 1.25
1.25 3.75 3.75
2.1875 4.0625 0.9375
2.1875 3.4375 1.5625
1.25 3.75 2.1875
1.25 4.6875 1.25
1.25 1.25 3.75
1.25 1.25 1.25
1.25 2.8125 1.25
0.3125 3.75 1.25
1.25 3.75 0.3125

Cells/Volumes

Domain/Cells/Volumes is a 1D float dataset of sized 15 (number of cell) [e.g. numpy.zeros(15,dtype=’f8’)] with data:

5.20833
2.60417
7.8125
7.8125
7.8125
15.625
1.30208
1.30208
2.60417
2.60417
15.625
15.625
2.60417
2.60417
2.60417

Connection/Areas

Domain/Connection/Areas is a 1D float dataset of sized 24 (number of connections/faces) [e.g. numpy.zeros(24,dtype=’f8’)] with data:

6.25
8.8388
6.25
6.25
3.125
6.25
6.25
6.25
6.25
2.2097
2.2097
2.2097
2.2097
2.2097
2.2097
2.2097
2.2097
2.2097
2.2097
6.25
6.25
2.2097
2.2097
2.2097

Connection/Cell Ids

Domain/Connection/Cell Ids is a 2D integer dataset of sized 24 (number of connections/faces x 2) [e.g. numpy.zeros((24,2),dtype=’i8’)] with data:

1 2
1 3
3 4
3 6
4 5
4 11
5 12
6 9
6 11
7 8
7 10
7 15
8 9
8 13
9 10
9 13
9 14
10 14
10 15
11 12
12 13
13 14
13 15
14 15

Connection/Centers

Domain/Connection/Centers is a 3D float dataset of sized 24 (number of connections/faces x 3) [e.g. numpy.zeros((24,3),dtype=’f8’)] with data:

4.16667 4.16667 3.3333
3.75 3.75 3.75
3.75 2.5 3.75
2.5 3.75 3.75
3.3333 1.6667 2.5
2.5 1.25 3.75
2.5 1.25 1.25
1.25 3.75 2.5
1.25 2.5 3.75
2.08333 3.75 1.25
2.08333 4.5833 1.25
2.08333 3.75 0.41667
2.08333 3.75 2.08333
2.08333 2.91667 1.25
1.25 4.48333 2.08333
1.25 2.91667 2.08333
0.41667 3.75 2.08333
0.41667 4.48333 1.25
1.25 4.48333 0.41667
1.25 1.25 2.5
1.25 2.5 1.25
0.41667 2.91667 1.25
1.25 2.91667 0.41667
0.41667 3.75 0.41667

Example script which convert and explicit unstructured grid in ASCII format to HDF5 format is available in the python source repository (see convert_explicit_ascii_to_h5.py).