[ICEM] T Junction Meshing using ICEM CFD

selvam2487 · November 11, 2012, 03:22

Hello,
I am new to ANSYS and I am currently learning meshing in ICEM CFD for my work on T Junction based flows. I have a few questions

1. What is the purpose of an O Grid? Is it only used at the boundaries? where can I learn more about the application of an O Grid?

2. The quality of mesh in the T Junction (where the two pipes intersect) where the important physics needs to be captured is average (It's related to my lack of understanding and using the blocking function properly). I have also posted some pictures which display the mesh along with the quality histogram. Any suggestion on how to improve the meshing functionality and reducing errors would be welcome. Thanks in advance.

Far · November 11, 2012, 05:11

Download from this link

https://dl.dropbox.com/u/68746918/pipejunction_3d.zip

selvam2487 · November 11, 2012, 06:33

Hello Mr. Far,

Thank you very much for your help. I think I understand the blocking strategy that you have implemented. I will try to do it and see what happens.

Regards,
Karthick

Far · November 11, 2012, 06:43

Just brief steps :

1. Create main block
2. split at the junction and then two splits on the two sides of small pipe and perpendicular to bigger pipe
3. delete two blocks on right and left of the small pipe
4. Make associations
5. snap vertices.
6. make o-grid inside the small small upto the large pipe's bottom. Select two extreme faces.
7. Make the O-grid for the larger pipe and again select the respective end faces.
8. go to edge mesh parameters and update all sizes and go to second tab and give size 2 and apply. Keep on applying until mesh size is at-least 20000 hexas
9.Check premesh.
10. One horizontal split in the large pipe.
11. Play with vertices location panel to adjust the blocking to higher quality.

Far · November 11, 2012, 14:35

Smooth mesh after applying the elliptical solver.

selvam2487 · November 12, 2012, 06:12

Hello Mr. Far,

Could you please explain me as to what is the function of an O Grid? Also, when checking premesh quality histogram, the angles are not good? How to improve the angles in the mesh? Also, for this T junction geometry, what are the other Premesh quality criterion that should be checked?

Regards
Karthick

Far · November 12, 2012, 06:28

Min angle is 32 and min quality is 0.6. which is good enough.

BrolY · November 12, 2012, 12:21

The O-Grid is very powerful because with this circular shape, O-Grid helps to have orthogonal cells around the circular shape.
Try to mesh a tube with, and without O-Grid, and it will be obvious

Far · November 12, 2012, 12:32

Mesh quality is 0.6 in ICEM and min orthogonal quality is 0.5 in Fluent and after smoothing (orthogonality) min mesh quality is 0.28 in ICEM and min orthogonal quality is 0.6 in Fluent.

Why smoothness decreases quality in ICEM and enhances the quality in Fluent?

What is the relationship between ICEM quality and Fluent orthogonal quality?

BrolY · November 12, 2012, 13:00

ICEM help manual about the quality :
Hexa

The quality is a weighted diagnostic between Determinant (between -1 and 1), Max Orthogls (normalized between -1 and 1; if deviation from orthogonality is greater than 90 degrees, then the normalized value will be smaller than 0) and Max Warpgls (normalized between 0 and 1; warpage of 0 degrees is 1, warpage of 180 degrees is 0). The minimum of the 3 normalized diagnostics will be used.

When you do orthogonal smoothing, you increase the orthogonal quality, but maybe, it also decreases the quality of your determinant.

I guess Simon could help us on that.

Far · November 12, 2012, 13:06

Check this Figure.

http://afinemesh.files.wordpress.com...el-529x359.png

Can you tell me which quality he is talking about?

Ralen · November 26, 2012, 08:16

Another idea.
1. Split selected block.
2. Split selected block.
3. Delete default associations of six edges and associate them to surface.
4. Snap Project Vertices.

Ralen · November 26, 2012, 08:18

5. Create O-Grid with all blocks and faces of three ends.

Far · November 26, 2012, 10:03

can you share the files?

By the way excellent comeback.

Far · November 26, 2012, 10:49

Ralen method is simple and somehow giving better quality and good looking mesh with few splits as you can see in attached pics(Mine in this post and Ralen' idea in next post.

My method:

Far · November 26, 2012, 10:51

Here are the images from Ralen's Method:

Ralen · November 27, 2012, 01:17

http://www.sendspace.com/file/p70hlf

vansyle · February 24, 2013, 22:09

Hi Ralen,
The link is died, could you please upload again? Thank you very much!

YoungMan · November 1, 2016, 19:35

Hello everyone, I this thread hasn't been used in two years but I would really appreciate it if someone could post a mesh file for a Tee junction for openfoam. It would really help with my work!

Far · November 2, 2016, 10:26

check these videos and you will find mesh and icem cfd files in description. if not i will provide you.

https://www.youtube.com/watch?v=HVbwUmGp3Xg

https://www.youtube.com/watch?v=aHVPJA0_JGQ

https://www.youtube.com/watch?v=-LOSmwUQcGI

https://www.youtube.com/watch?v=fycZjB2txig

https://www.youtube.com/watch?v=u7a9C2zo0zg

November 11, 2012, 06:33	thank you	#3
selvam2487 Member Karthik Join Date: Oct 2012 Location: Germany Posts: 53 Rep Power: 14	Hello Mr. Far, Thank you very much for your help. I think I understand the blocking strategy that you have implemented. I will try to do it and see what happens. Regards, Karthick

November 11, 2012, 06:43		#4
Far Senior Member Sijal Join Date: Mar 2009 Location: Islamabad Posts: 4,558 Blog Entries: 6 Rep Power: 54	Just brief steps : 1. Create main block 2. split at the junction and then two splits on the two sides of small pipe and perpendicular to bigger pipe 3. delete two blocks on right and left of the small pipe 4. Make associations 5. snap vertices. 6. make o-grid inside the small small upto the large pipe's bottom. Select two extreme faces. 7. Make the O-grid for the larger pipe and again select the respective end faces. 8. go to edge mesh parameters and update all sizes and go to second tab and give size 2 and apply. Keep on applying until mesh size is at-least 20000 hexas 9.Check premesh. 10. One horizontal split in the large pipe. 11. Play with vertices location panel to adjust the blocking to higher quality. Anouar and ticofiz like this.

November 12, 2012, 12:21		#8
BrolY Senior Member AB Join Date: Sep 2009 Location: France Posts: 323 Rep Power: 22	The O-Grid is very powerful because with this circular shape, O-Grid helps to have orthogonal cells around the circular shape. Try to mesh a tube with, and without O-Grid, and it will be obvious selvam2487 likes this.

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November 12, 2012, 06:12		#6
selvam2487 Member Karthik Join Date: Oct 2012 Location: Germany Posts: 53 Rep Power: 14	Hello Mr. Far, Could you please explain me as to what is the function of an O Grid? Also, when checking premesh quality histogram, the angles are not good? How to improve the angles in the mesh? Also, for this T junction geometry, what are the other Premesh quality criterion that should be checked? Regards Karthick

November 12, 2012, 06:28		#7
Far Senior Member Sijal Join Date: Mar 2009 Location: Islamabad Posts: 4,558 Blog Entries: 6 Rep Power: 54	Min angle is 32 and min quality is 0.6. which is good enough.

November 12, 2012, 12:32		#9
Far Senior Member Sijal Join Date: Mar 2009 Location: Islamabad Posts: 4,558 Blog Entries: 6 Rep Power: 54	Mesh quality is 0.6 in ICEM and min orthogonal quality is 0.5 in Fluent and after smoothing (orthogonality) min mesh quality is 0.28 in ICEM and min orthogonal quality is 0.6 in Fluent. Why smoothness decreases quality in ICEM and enhances the quality in Fluent? What is the relationship between ICEM quality and Fluent orthogonal quality?

November 12, 2012, 13:00		#10
BrolY Senior Member AB Join Date: Sep 2009 Location: France Posts: 323 Rep Power: 22	ICEM help manual about the quality : Hexa The quality is a weighted diagnostic between Determinant (between -1 and 1), Max Orthogls (normalized between -1 and 1; if deviation from orthogonality is greater than 90 degrees, then the normalized value will be smaller than 0) and Max Warpgls (normalized between 0 and 1; warpage of 0 degrees is 1, warpage of 180 degrees is 0). The minimum of the 3 normalized diagnostics will be used. When you do orthogonal smoothing, you increase the orthogonal quality, but maybe, it also decreases the quality of your determinant. I guess Simon could help us on that.

November 12, 2012, 13:06		#11
Far Senior Member Sijal Join Date: Mar 2009 Location: Islamabad Posts: 4,558 Blog Entries: 6 Rep Power: 54	Check this Figure. http://afinemesh.files.wordpress.com...el-529x359.png Can you tell me which quality he is talking about?

November 26, 2012, 10:03		#14
Far Senior Member Sijal Join Date: Mar 2009 Location: Islamabad Posts: 4,558 Blog Entries: 6 Rep Power: 54	can you share the files? By the way excellent comeback.

February 24, 2013, 22:09		#18
vansyle New Member df Join Date: Oct 2012 Posts: 4 Rep Power: 14	Hi Ralen, The link is died, could you please upload again? Thank you very much!

November 1, 2016, 19:35		#19
YoungMan New Member Dan Join Date: Sep 2016 Posts: 2 Rep Power: 0	Hello everyone, I this thread hasn't been used in two years but I would really appreciate it if someone could post a mesh file for a Tee junction for openfoam. It would really help with my work!

November 2, 2016, 10:26		#20
Far Senior Member Sijal Join Date: Mar 2009 Location: Islamabad Posts: 4,558 Blog Entries: 6 Rep Power: 54	check these videos and you will find mesh and icem cfd files in description. if not i will provide you. https://www.youtube.com/watch?v=HVbwUmGp3Xg https://www.youtube.com/watch?v=aHVPJA0_JGQ https://www.youtube.com/watch?v=-LOSmwUQcGI https://www.youtube.com/watch?v=fycZjB2txig https://www.youtube.com/watch?v=u7a9C2zo0zg