NPARC Interface

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The ICEM-CFD/NPARC interface writes an input file and a grid file for the NPARC flow solver version 3, from a 2D or 3D multiblocks structured grid created with MULCAD or with the HEXA-Mesher. This interface provides an option to automatically create the overlapps at block interfaces.

The NPARC input file controls how the NPARC program is executed. It contains the following sections:

The variables of the namelist BLOCK and the block boundary conditions can be defined for each domain. NPARC solvers parameters included in the INPUT and TURBIN Namelists may be edited and stored using the NPARC Graphical User Interface.

The grid file is written in the multiblocks Plot3D format. The user has the option to write the grid file in single precision Fortran-unformatted (binary) or formatted.

For more information on NPARC, please refer to the NPARC Alliance Website.

Creating the NPARC input file and grid file

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

In MULCAD, the block parameters and boundary conditions are defined in the "Unspec. Bound. Cond. " menu and in the DDN-Mesher Interface, in the "general bound. cond." menu. Please refer to the General Remarks section for more details.

Block Parameters:

In MULCAD, the block parameters must be defined on domains. After choosing a domain, select the menu item FLAG and enter the character string BLOCK. The remaining variables of the boundary conditions menu are used to specify the different block parameters for NPARC (see table below).

For grids generated with the HEXA-Mesher, the block parameters are defined on families. They should be applied to 2D-families for 2D models, and to 3D families for 3D models. After selecting a family, set the variable string1 to BLOCK, then use the remaining variables of the boundary conditions menu to specify the different block parameters for NPARC. The following table indicates which fields of the general boundary condition menu serve to define the NPARC block parameters. 

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 MULCAD       DDN-Mesher       NPARC        Type     default
                             parameter                value
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 2. NR        3. integer      invisc(1)    integer      1
 3. VALUE     4. real1        invisc(2)    integer      1
 4. X         5. real2        invisc(3)    integer      1
 5. Y         6. real3        lamin(1)     integer      0
 6. Z         7. real4        lamin(2)     integer      0
 7. SCALE     8. real5        lamin(3)     integer      0
 8. A         9. real6        cofmix        real        0.09
 9. B        10. real7        dtblk         real        0.0
10. C        11. real8        gamma         real        1.4
11. D        12. real9        dis2          real        0.25
12. ATTRIB    2. string2      dis4          real        0.64
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Note that for a 2D model, the parameters invisc(3) and lamin(3) are not written in the NPARC input file and therefore need not to be specified. The default values listed above are written for each block in the input file unless the block parameters are defined by the user. The value of dis4 is written in a character field (ATTRIB) and is limited to 5 characters.

Boundary Conditions:

In MULCAD, the boundary conditions must be defined on the edge entities for a bidimensional model and on the subfaces for a tridimensional model. After selecting a topological entity (edge or subface), define the boundary condition using the general boundary condition menu. The table below gives the correspondance between the variables in the MULCAD boundary condition menu and the NPARC variables.

For grids generated with the HEXA-Mesher, the boundary conditions are defined on edge-families for 2D models, or on face-families for 3D models. After selecting a family, define the NPARC variables in the general boundary condition menu. The following table indicates which fields of the general boundary condition menu serve to define the NPARC boundary condition parameters. Note that the translator creates by default a type 77 boundary segment at each undefined bloc interface.

For more details on how to set boundary conditions for the NPARC flow solver, please refer to the "NPARC User Manual". 

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 MULCAD       DDN-Mesher       NPARC        Type     default
                              variable                value
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 2. NR        3. integer      itype        integer      0
 4. X         5. real2        press         real        0.0
 5. Y         6. real3        temp          real        0.0
 6. Z         7. real4        edge         integer      0
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By default, the boundary type is set to 70 on overlapped block interfaces,  77 on abutting block interfaces,  50 on walls (slip surface), and  81,82 or 83 on singularities.

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