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-   -   non-positive volumes (http://www.cfd-online.com/Forums/fluent/27853-non-positive-volumes.html)

Javier Fernandez August 23, 2000 05:47

non-positive volumes
 
I am a fluent new user and I have same problems with non-positive volumes. I would like to know if it is posible to repair a mesh whith this kind of troubles by means of the "adapt" menu or I will have to remesh my geometry. Thanks.

Sandeep August 23, 2000 10:37

Re: non-positive volumes
 
You can first try and fix this problem inside of the fluent solver by doing a repair-facehandedness command:

grid > modify-zone > rfh

After you do this, see if any negative volumes still show up. If they still do, you will have to go back to the pre-processor and adjust the mesh density.

Angus Duncan August 23, 2000 10:50

Re: non-positive volumes
 
I have had this problem with tgrid a while back. The repair was simply to save the mesh and then re-read it back into tgrid. A mesh check should then run okay and you can save and export this mesh to Fluent.

If the non-positive volume problem is due to left-handed faces then use this command in the console: %repair-face-handedness. Again, a mesh check should confirm the problem is fixed.

I am not sure if these 'fixes' can be applied in Fluent 5- I guess you're using Gambit. It's worth a try.

Angus

Max Nutini August 23, 2000 10:52

Re: non-positive volumes
 
I sometimes have the same problem in 2d axysimmetrical cases where the axis is y=0. In that case it is enough to translate the whole domain of a negligible quantity (Dy = 0.001 for instance). See if this is your case... Bye Max

Javier Fernandez August 24, 2000 04:16

Re: non-positive volumes
 
Thank you all for information. It was very useful

Desmond Hui August 29, 2000 00:37

Re: non-positive volumes
 
Hi,

For Non-positive volumes, I have the following suggestion to you.

Use Iso adaption to locate the cell of negative volumn and then use gambit to modify the mesh.

yours, Desmond


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