GASP Interface

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The translator creates an input file, a grid file and a solution file in the GASP format. The input file is written in ASCII and contains the topology and the boundary condition information. The grid and solution files are written in binary.

This translator supports 2D or 3D configurations composed of one or several blocks. It handles non-C0 contiguous interfaces between blocks allowing local refinement. For 2D grids, the interface generates the third dimension (one cell thick) automatically. Note that it is assumed that the grid lies on the z=0 plane and that all surfaces normals point toward the Z+ direction.

Creating the GASP Input Files

The translator writes the GASP input file using structured domain files (domain.1 to domain.n), the boundary condition file (boco) and the topology file (topo_mulcad_out). To create the GASP input file, select the translator "GASP" in the "Output" menu from the ICEM CFD/CAE Manager. After clicking "Write output" you can specify options for the GASP interface:

The interface generates the GASP files 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 condition for GASP

In MULCAD the boundary conditions are defined using the "Unspec. Bound. Cond." menu. For grids generated with the HEXA-Mesher, the boundary conditions are defined in the "general bound. cond." menu of the DDN-Mesher Interface. Please refer to the GENERAL REMARKS section for more details.

In 3D, the boundary condition types (bctype) are recognized on faces only, except for singular faces where bctype are defined on the corresponding edges. For a bidimensional grid, the bctype are defined on the edges or the vertices corresponding to singular edges. To define a boundary condition for GASP, simply select a face, edge or vertex and give it a boundary condition type: 

        MULCAD          DDN-Mesher
        ------          ----------
        1.FLAG           1.string1        Enter the word TYPE
        2.NR             3.integer        Enter the bctype number

GASP recognizes the following boundary condition types: 

  -1  Fixed at free-stream values, q_inf
  -2  Fixed at input profile
  -3  First order extrapolation
  -4  Second order extrapolation
  -5  Riemann invariants (subsonic)
  -6  p0, T0 fixed (inflow), pback fixed (outflow) (subsonic)
   8  Tangency
   9  No-Slip, adiabatic
  10  No-slip, T = tWall
 -11  Y-Z plane zonal boundary correction
 -12  Z-X plane zonal boundary correction
 -13  X-Y plane zonal boundary correction
 -14  X-axis singular (axi-symmetric)
 -15  Y-axis singular (axi-symmetric)
 -16  Z-axis singular (axi-symmetric)
 -17  Y-Z plane symmetry
 -18  Z-X plane symmetry
 -19  X-Y plane symmetry
 -20  Zonal Boundary
  21  -pi/80 axi-symmetric wall
  22  +pi/80 axi-symmetric wall
  26  No-slip, catalytic, T = tWall
  27  No-slip, pointwise T = tWall
  28  No-slip, catalytic, pointwise T = tWall

Note that by default, the translator assigns bctype=-20 for all block interfaces and bctype=-3 for all walls.

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