I have a problem of :"non-positive volume" when I want to iterate. what does it mean? (I work with a 2d model!)

You may have meshing problem. Check youe DBS file by GAMBIT.

Sincerely, Jinwook

I have seen this problem occur most times with pretty skewed meshes that have been smoothed in Gambit.

1. The first step as soon as export your mesh in to Fluent is to do a grid check. 2. If you have a no positive volume. (In your case for a 2d problem, its non positive area.) 3. Grid check indicates u have a non positive area. 4. All this indicates is you don't have a quality mesh and your mesh contains inverted elements. 5. Get back to Gambit land or your preprocessor land and try obtaining a decent mesh. 6. For a 2d problem this should be trivially simple.

Sundar

thank you very much for your answers

Actually, I use a moving mesh model, and I have noticed that for the 1st mesh, it is ok, but when I start the iterations for the unsteady problem, I have this problem of non-positive volume (confirmed by the grid check)

Can anyone help me about these problems of non-positive volumes with moving meshes?

There is a limitation of using deforming mesh in FLUENT. It can't solve the problem with too large deformed meshes. Otherwise your mesh skewness will exceed the tolerance of the FLUENT. The only way is to rebuild your deformed meshes to minimize the mesh skewness.

I guess your problem connected to the requirement that the interfaces between zones moving relatively to each other have to be completely indepentend. In other words, even no single vertex must be shared by both interfaces. (use DISCONNECT VERTICES in GAMBIT)

Yours sincerely, Markus

[roger_pn]

Originally Posted by Emilien
;100797

I have a problem of :"non-positive volume" when I want to iterate. what does it mean? (I work with a 2d model!)

I'm trying to export a 3D mesh to Fluent but it says that i have non-positive volume and that the minimum volume value is negative. What does this mean??

I've tried to smooth all volumes and to check the validity of them and it says all volumes are valid. So i don't know why i have a negative volume. I'm meshing a rear wing of a World series by renault car (simulating the ailerons and the wind tunnel).

Thank u for the help.