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-   -   [ANSYS Meshing] Volume Orientation Problem (http://www.cfd-online.com/Forums/ansys-meshing/109112-volume-orientation-problem.html)

Kentin November 9, 2012 09:55

Volume Orientation Problem
 
1 Attachment(s)
Hello everybody!

Here is my problem :
Attachment 16808

As you can see on this picture, it shows a draft tube pier. I use o-grid and an hexa meshing.
After an ICEM checkMesh, it informs me that negative volume are present on this part. I tried many stuff to fix the problem but it unfortunately did not come off.

I wil be very glad to have some help,

Kentin

Far November 9, 2012 11:12

what do you mean by negative orientation? is it negative quality?

Negative orientation : Blocking > Edit Block > Change Block IJK

Negative quality : Improve blocking

Kentin November 9, 2012 11:32

Negative volumes are defined when i do a Blocking->Pre-Mesh Quality (criterion determinant 3*3) between -1;1.
I find volumes below 0 with this criteria, concentrated on pier nose (see picture in my first post).

Once again, i find these volumes when i do a checkMesh with option createSubset. I Volume Orientation Subset is created and means that i have an error here. I tried to unrefine mesh and other things but i did not find solutions to solve this volume orientation problem.

If you have any idea...
Thanks a lot,

Kentin

diamondx November 9, 2012 18:45

make sure edge bunching law all same for all parallel edges.
Use scan edge to see where does the problem come.
You may share your project, i can take a look at it...

Kentin November 12, 2012 10:53

I checked all parallel edges and did not find anything special.
Same thing for scan planes, actually first picture i posted came from a scan. And as you can see, there is no special thing visible..
If you have any others ideas to check meshing, i ll be very glad to hear it!

Quentin

diamondx November 12, 2012 11:31

sometime for a simple update of the pre-mesh can help solve the problem. Would you mind sharing your project. i can take a look at it. Thanks

Aysiyi November 13, 2012 06:01

in my mind, if you have some negative volumes, maybe you have some problem association ,you shoud see the edge association

Kentin November 13, 2012 13:09

Thanks but i finally found the solution.

In blocking->check Blocks->Fix Inverted Blocks, very usefull tool! No negative volume anymore.

Thanks for all your advices.

Kentin

Far November 13, 2012 13:31

Quote:

Originally Posted by Far (Post 391287)
what do you mean by negative orientation? is it negative quality?

Negative orientation : Blocking > Edit Block > Change Block IJK

Negative quality : Improve blocking

Are u talking about change block IJK?

Kentin November 14, 2012 04:01

Negative orientation is not negative quality but negative volume specified by 3*3 determinant quality.
I found the solution thanks to this post :
http://www.cfd-online.com/Forums/cfx...-icem-cfd.html
I just used the tool i notice in my last post..


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