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prapanj March 10, 2008 19:24

2D unstructured Grid

I am writing a 2D unstructured Euler solver.

I am willing to take in the grid in plot3D format. The grid generation software I have is gridgen. Could someone guide me in doing this?

I find that the plot3D option is not getting highlighted when i tend to export points. I found that this is dependent on the analysis software choice.

I had created block. but since it is only one face, when i export the grid points, I am only having the domain option highlighted, the block option is dim.

It would be kind of you if you could suggest some other 2D unstructured grid format too. I had tried other formats, but I am not able to get info on the formats on the net. Without format info I would not be able to read the grid into my program.

Please help.

Thankin you


Praveen. C March 11, 2008 04:12

Re: 2D unstructured Grid
Isnt plot3d a structured grid format ? Do you want to convert it into unstructured grid ? Some unstructured grid formats I have used are amdba and msh. See for example the softwares BAMG and GMSH which export in msh format.

John Chawner March 15, 2008 09:14

Re: 2D unstructured Grid
Hello Prapanj,

PLOT3D is a file format restricted to structured quad grids (i.e. a mapped mesh). So, if you select any unstructured grids, PLOT3D isn't an available option.

Also, Gridgen lets you export either the grid by itself or the grid as formatted for your CFD solver. The latter requires blocks to exist.

The easiest way to export grids to PLOT3D is this...

1. Input/Output Commands

2. Grid Pts - Export

3. Domain - Surfaces

4. Enter the file name.

5. On the File Attributes menu, select PLOT3D and any other attributes.

6. Select the domains to export.

If you have 2D blocks and want to export the assembled domains as the block face, do this...

1. Analysis Software Commands

2. Select Analysis Software

3. Choose a CFD Solver and set it to 2D.

4. Create all your domains.

5. Assemble those domains into blocks (2D blocks have only 1 face each).

6. Input/Output Commands

7. Grid Pts - Export

8. Block - Volumes

9. Enter the file name.

10. On the File Attributes menu, select PLOT3D and any other attributes.

11. Select the blocks to export.

Hope this helps.

prapanj March 15, 2008 17:30

Re: 2D unstructured Grid

thank you for your response. I am writing a solver on my own. And I found that Cobalt would be the best format. So I have started using that format. From the edge connectivity info that cobalt format has, I have written a fortran 90 subroutine to get the cell node connectivity too. I would like upload that to the cfd-online page, if you feel that would be of any use.

Thanking you


John Chawner March 15, 2008 18:01

Re: 2D unstructured Grid
Hello parpanj,

I'm glad you've got something working. I also suggest that you consider using the CGNS file format standard. See the web site This is an open format for not only grid information but all the solver information too. The library is freely available on the web site. CGNS might work better for you than adopting a commercial vendor's format as your own. Plus, your files would be immediately compatible with all other CGNS compatible tools.

Best regards.

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