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-   -   Boundrycondition problem between Gambit and Fluent (https://www.cfd-online.com/Forums/fluent/42684-boundrycondition-problem-between-gambit-fluent.html)

 smalawi October 29, 2006 05:21

Boundrycondition problem between Gambit and Fluent

Hi all,

i'm working with a freind on modeling a premixed burner in Gambit. So far we gnenrated the mesh in Gambit and specified the boundry conditions.

the burner has to inlets, one for fuel gas which is velocity spec and the other is for air and was set to pressure inlet in gambit. there is also a combined outlet, which is set to pressure outlet. in both caese we specified the faces for the boundry type with no problems.

after exproting the mesh in Fluent, we can olny see the wall, interior and outlet. the fuel inlet and air are both messing.

what is the problem here? how to fix it?

I'm used on solving only 2D problems and never had this issue before, my freind has no clue?

cheers,

sm

 Jason October 30, 2006 09:07

Re: Boundrycondition problem between Gambit and Fl

It sounds like the faces you defined BCs on weren't part of the meshed volume. Check your connectivity. Another common reason is that there are two volumes (one being a copy of the other)... and when you meshed, Gambit picked the first volume, but when you went to define your BCs, Gambit picked the second volume... The next common problem is that surfaces picked for inlets were already picked as walls... I believe Gambit leaves the first BC that was assigned and ignores the second.

Check those things first, and if you can't find the problem, then post more information about your problem (like how you built the geometry).

Hope this helps, and good luck, Jason

 smalawi October 30, 2006 22:52

Re: Boundrycondition problem between Gambit and Fl

Thanks Jason for the tips,

I checked the volumes and I only have one. I used the tri mesh for meshing the volume directly without any other adjustments. I deleted the boundary conditions and reworked them so that I select the faces I want by name and cross checking any overlap, there was non.

I exported the mesh to fluent and still had the same problem; both inlet boundary conditions were not visible. Only interior, wall (or new wall), and the outlet, I suspect that fluent is combining the other boundaries with the wall and renaming them new wall. I do not know how to fix this. Can you think of something?

i created the volume as follows:

1. Created vertices in gambit to generate the 2D face, which I used later on without problems. 2. meshed the 2D face and created the boundary conditions 3. saved the file. 4. removed the old mesh 5. Created the 3D volume by rotating the 2D mesh around the x axis (360 deg). 6. meshed the volume directly with tri mesh 7. Removed the old boundary conditions and created new ones for the new faces 8. exported the mesh to fluent and it looks good except for the boundary conditions?

Appreciate any help that I can get on this issue. I tried with my friend to create another 3D model to verify the software, basically a cylinder tube directly and used it in fluent without problems?

 Nikhil October 31, 2006 13:21

Re: Boundrycondition problem between Gambit and Fl

even i am having similar types of problems i cant find the the boundary conditions that i applied in gambit in Fluent. i think there might be an easier way to get around this problem. will really appreciate if somebody can give some tips to get around this problem.

Thanks in advance for the response Nikhil

 Jason October 31, 2006 15:57

Re: Boundrycondition problem between Gambit and Fl

Under solver, make sure Fluent 5/6 is selected before defining BCs. Other than that, the only thing I can think of is to start from scratch (instead of starting from the 2D geometry). There may be something weird still attached to some of the geometry... even though you delete the BCs Gambit might not realize it when you switch from 2D BCs to 3D BCs. The face may still think it has a "fluid volume" BC attached to it when from when it exported the 2D mesh... or one of the edges may still think it's a wall or something.

You might want to support a ticket to your Fluent support too (if you're able to... I know sometimes having access to Fluent support is difficult if you're in a university)... this could be a bug and they may or may not have a fix for it.

Hope this helps, and good luck, Jason

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