[ANSYS Meshing] Volume Orientation Problem

Kentin · November 9, 2012, 08:55

Hello everybody!

Here is my problem :
pier.jpg

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, 10:12

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, 10:32

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, 17:45

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, 09:53

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, 10:31

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, 05:01

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, 12:09

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, 12:31

Quote:

Originally Posted by Far

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, 03:01

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..

November 9, 2012, 08:55	Volume Orientation Problem	#1
Kentin New Member Kentin cal Join Date: May 2012 Posts: 11 Rep Power: 13	Hello everybody! Here is my problem : pier.jpg 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

November 9, 2012, 17:45		#4
diamondx Super Moderator Ghazlani M. Ali Join Date: May 2011 Location: Tokyo, Japan Posts: 1,385 Blog Entries: 23 Rep Power: 28	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... __________________ Regards, New to ICEM CFD, try this document --> https://goo.gl/KAOIwm Ali

November 12, 2012, 10:31		#6
diamondx Super Moderator Ghazlani M. Ali Join Date: May 2011 Location: Tokyo, Japan Posts: 1,385 Blog Entries: 23 Rep Power: 28	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 __________________ Regards, New to ICEM CFD, try this document --> https://goo.gl/KAOIwm Ali

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November 9, 2012, 10:12		#2
Far Super Moderator Sijal Join Date: Mar 2009 Location: Islamabad Posts: 4,552 Blog Entries: 6 Rep Power: 53	what do you mean by negative orientation? is it negative quality? Negative orientation : Blocking > Edit Block > Change Block IJK Negative quality : Improve blocking

November 9, 2012, 10:32		#3
Kentin New Member Kentin cal Join Date: May 2012 Posts: 11 Rep Power: 13	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

November 12, 2012, 09:53		#5
Kentin New Member Kentin cal Join Date: May 2012 Posts: 11 Rep Power: 13	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

November 13, 2012, 05:01		#7
Aysiyi Member aysiyi Join Date: Nov 2012 Posts: 40 Rep Power: 12	in my mind, if you have some negative volumes, maybe you have some problem association ,you shoud see the edge association

November 13, 2012, 12:09		#8
Kentin New Member Kentin cal Join Date: May 2012 Posts: 11 Rep Power: 13	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

November 14, 2012, 03:01		#10
Kentin New Member Kentin cal Join Date: May 2012 Posts: 11 Rep Power: 13	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..