DSMC-SANDIA Interface

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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:

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 Shell".

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:

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.

        MULCAD                                                   Default
        ------                                                   -------
        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:

  1. Only 2D models -single or multiblock- are supported by the interface.
  2. 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.
  3. Each edge must be composed of only 1 segment.
  4. The normal of all subfaces must point toward the z+ axis.
  5. 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.
  6. 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.
  7. 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 hold anymore.
  8. A boundary condition must be defined for each side except for interface edges where a boundary type 7 is given by default.

N.B. The actual version expects a maximum of six adjacent regions per side.

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