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doki July 10, 2010 06:37

3D catia models to gambit
I am trying to import a 3D catia model into gambit using .igs or .stp formats.
when I intend to mesh the geometry, I realize that there are a lot of small edge/faces in the geometry; which makes it impossible to generate a suitable mesh.
how can I fix the problem so that I could get proper mesh?

Hari Prasad July 10, 2010 08:05

Hi Doki,
It sometimes happens that when you import geometries to gambit there is a duplication of edges and faces particularly edges common to several faces and faces common to several volumes. Click on every edge and face individually and check if there are several duplicates overlapping. Retain only one edge or face and remove the rest that are overlapping and try meshing it.It should work hopefully.Good Luck!!:):)

doki July 10, 2010 10:00

face or edge duplication sure does have effect on the geometry, but another source of problem is (I think) some tolerance problems or even the nature of such formats.
I tried to check the geometry and I realized that there are many "broken" edges/faces in the volume. to repair all of these edges, is a time consuming task; and I do not know what to do.

Hari Prasad July 11, 2010 09:37

If your model is not too complex you can try modelling it on gambit itself.

kdrbrk July 13, 2010 03:10

Hi doki, can you share your CATIA model here? or at least some photos?
Make display "shading with edges" option.

doki July 13, 2010 06:42

unfortunately because of internet issues it is impossible for me to do so.
But as far as I have checked, the model has no problems in native software.
I have also tried to use a 3rd software (e.g. solidworks) to get a .sat geometry file. but there still remain some problems.

kdrbrk July 13, 2010 07:20

Maybe CATIA created some little faces.
ex: when I try to make a fillet of an airfoil, sometimes it creates very small faces depending on the fillet radius. its very annoying but there is nothing to do. I try making geometries as simple as I can.

arash_7444 July 13, 2010 10:07

Try to clean up your geometry (i.e. click pad "tools" )

I use ProEngineer to create geomtery because it is easier to import them to GAMBIT. I mean gambit can read *.prt and you don't need to convert it to *stl *.igs

good luck

doki July 16, 2010 07:57

I did indeed do so. but the problem still remains in the geometry:(

Chris D July 16, 2010 10:20

Have you tried to clean up the geometry with your cad program before importing it into gambit? You might be able to simplify your geometry by removing small features that unnecessarily complicate your cfd model. By doing this, you give gambit a smaller chance of screwing up, which is always a good thing!

doki July 16, 2010 12:44

sure I have checked it. But as I mentioned above, the geometry does not show any problems in the native software.
And Ofcourse I have performed some simplifications in order to get a simpler model for grid generation. it seems there should be something related to the extension.

Chris D July 16, 2010 14:00

Is there a reason you're limited to .igs and .stp? I've had pretty good luck importing parasolid into gambit.

doki July 17, 2010 01:44

I have used .sat extensively for such cases. but catia does not support that extension in its normal interface, so I tied other extensions.
So which extension would you recommend me to use? the model is developed in catia v5r18.

Chris D July 17, 2010 08:41

The extension for parasolid is .x_t. I'm not sure if you can save as parasolid with catia, but I know you can with solidworks.

doki July 17, 2010 11:21

you are right.
solidworks can export the .sat (ACIS) extension too. but I can not find any suitable extension to send catia geometry to solidworks. the stp and igs extensions do affect the geometry the same way as what they do in Gambit.

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