The DSMC-SANDIA interface writes an input file from an ICEM
CFD/CAE surface grid and its attached boundary conditions in the
format read by the DSMC-SANDIA solver.
Creating the DSMC-SANDIA Input File
The translator writes the SANDIA input file using the
structured domain file(s) from PADAMM (domain.1 to domain.n), the
index files from PADAMM (index1 to indexn), the boundary
condition file from MULCAD (boco), and the topology file from
MULCAD (topo_mulcad_out). To create the input file, select the
translator "DSMC-Sandia" in the "Output" menu
from the ICEM CFD/CAE Manager. After clicking "Write
output" you can specify options for the interface:
- give the name of the boundary condition file
(default is configuration/parts_mesh/mesh/boco)
- give the name of the topology file
(default is configuration/topology/topo_mulcad_out)
- give the name of the SANDIA-DSMC input file
(default is configuration/parts_mesh/transfer/configuration)
The interface generates the input file located in the Transfer
Shell. You may open a shell window in this directory by selecting
the menu items "Utility" and "Transfer
Defining boundary conditions for DSMC-SANDIA in MULCAD
The boundary conditions are defined using the
"Unspecified Bound. Cond." menu in MULCAD. In this menu
the user can specify the boundary conditions on each edge of the
model. Please refer to the General Remarks section
for more details.
Boundary Type Code:
The available boundary type codes for sides 1 through 4 are:
- 1: Line of symmetry
- 3: Free stream bound. cond. (constant values)
- 3x: Free stream bound. cond. (variable values
using subroutine bc).
x indicates appropriate table entry to use from
If 3x>0, use x in table. Else use y,
radial source line.
- 4: Free stream bound. cond. (reflective-subsonic) single
- 5: Solid surface
- 7: Connection to another region
- 8: Outflow (non-reentrant)
- 9: Porous wall (extra bc in input)
- 10: Outgassing surface
The boundary type code must be specify under NR in the
boundary condition menu. If a type 5, 5x or 10 is chosen,
additional boundary conditions can be specified. These correspond
to the entries in the BC table of the DSMC-SANDIA input file: Spec.
refl., Temp. K, Material #, and Value. Finally, the
maximum cell weight needs also to be defined in this menu, under
the entry SCALE(7). A default value of 300 is given for
the maximum cell weight. This value can be changed here while
setting the boundary conditions.
2.NR Enter the boundary type code (see table above)
3.VALUE If applicable, enter Spec. Refl. 0.0
4.X If applicalbe, enter Temp. K 273.0
5.Y If applicable, enter Material # 0
6.Z If applicable, enter Value 0.0
7.SCALE Enter the maximum cell weight 300
How to build the model in MULCAD
A serie of rules must be carefully followed when constructing
the model in MULCAD:
- Only 2D models -single or multiblock- are supported by
- Each region must be composed of 4 edges. These edges can
be shared with other regions as long as the edge meshing
is the same for both regions. For adjacent regions with
different edge meshing, edges can not be shared. This
means that for a model composed of 5 regions, the MULCAD
model would have 20 edges.
- Each edge must be composed of only 1 segment.
- The normal of all subfaces must point toward the z+ axis.
- The x-axis is assumed to be oriented from the left to the
right and the y-axis from the bottom to the top. The
order of the global points are calculated accordingly.
- The sides are grouped by pair: the lower and upper sides
forming pair 1-3 and the left and right sides forming
pair 2-4. A pair of sides can be either linear or
circular. That is, if side 1 is an arc, side 3 must also
be an arc.
- The sides can make an angle with the x-y axis. However,
they must not exceed a 45 deg. angle deviation. For
example, side 1 which is along the x-axis can form a max
angle of 44.9 deg. with the axis. Above that, the
definition of the lower/upper left/right corners does not
- A boundary condition must be defined for each side except
for interface edges where a boundary type 7 is given by
N.B. The actual version expects a maximum of six adjacent
regions per side.