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July 9, 2012, 14:50
Why don't we use domain interface to solve this problem?
#1
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lnk
Join Date: Feb 2011
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Hi,

May I ask you a question about O-grid generation? Here is a picture. I'd like to generate a picture like B. But since I can't rotate my block, I always obtain A. How to solve this problem?

Best regards and many thanks,
lnk
Attached Images
 O-grid.jpg (19.5 KB, 38 views) block.jpg (53.8 KB, 47 views)

Last edited by lnk; July 18, 2012 at 15:35.

 July 9, 2012, 15:14 #2 Super Moderator   Sijal Join Date: Mar 2009 Location: Islamabad Posts: 4,285 Blog Entries: 6 Rep Power: 43 what u want to do?

 July 9, 2012, 15:49 #3 Super Moderator   Sijal Join Date: Mar 2009 Location: Islamabad Posts: 4,285 Blog Entries: 6 Rep Power: 43 A=B. So it does not make any difference.

July 9, 2012, 16:20
#4
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lnk
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Quote:
 Originally Posted by Far A=B. So it does not make any difference.
Here is the problem. The geometry I'd like to mesh is a connection of a tube with a cube. If I have the O-grid like A, I can't correct the bad quality meshes at the connection part of the tube and cube. So I try to rotate the O-grid to solve this problem.

Best regards and many thanks,
lnk
Attached Images
 block.jpg (53.0 KB, 26 views) quality.jpg (51.3 KB, 29 views) surface.jpg (50.8 KB, 32 views) mesh.jpg (60.9 KB, 31 views)

 July 10, 2012, 02:31 #5 Super Moderator   Sijal Join Date: Mar 2009 Location: Islamabad Posts: 4,285 Blog Entries: 6 Rep Power: 43 This is easy case for ICEM Hexa. If you can share your files, we can give a quick try.

 July 10, 2012, 04:38 #6 Senior Member   AB Join Date: Sep 2009 Location: France Posts: 323 Rep Power: 14 just create points at the 2 exits of your model and associate the vertices of your o-grid to modifiy its shape. Then align the internal vertices of your o-grid with the vertices of the 2 exits of your model and you are all good !

July 10, 2012, 06:30
#7
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lnk
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Quote:
 Originally Posted by Far This is easy case for ICEM Hexa. If you can share your files, we can give a quick try.
Here is my file. Thanks you very much!

Best,
lnk
Attached Files
 abc.zip (53.9 KB, 5 views)

Last edited by lnk; July 11, 2012 at 05:15.

July 10, 2012, 08:10
#8
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lnk
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Quote:
 Originally Posted by BrolY just create points at the 2 exits of your model and associate the vertices of your o-grid to modifiy its shape. Then align the internal vertices of your o-grid with the vertices of the 2 exits of your model and you are all good !
What do you mean by 'exits'? Won't that change my geometry?

 July 10, 2012, 23:50 #9 Super Moderator     Ghazlani M. Ali Join Date: May 2011 Location: Tokyo, Japan Posts: 1,366 Blog Entries: 23 Rep Power: 21 Far, Broly. this geometry is not easy...very tricky... i've been fighting with it for more than 4 hours now.i thought may be li's strategy for blocking was incorrect, so i erased his blocking and tried to came up with a better one using bottom-up approach. I couldn't, then i came back to li's blocking, realized that he can never get a good quality because he needs ygrid when the arc's circle meets the tangent line, alse noticed that geometry needs some cleanup, there are additional surfaces inside (tube), maybe that's why. I don't understand why and how li did that blocking... i need a break. i hope i can wake up the morning and find your approaches... @li i'll come back to your geometry tomorrow to finish it... i saw another thread where you're asking about ygrid, you have to merge before, and select the triangular shape, but i just don't know how you can do that with your blocking... __________________ Regards, New to ICEM CFD, try this document --> https://goo.gl/NEbygB Ali

 July 10, 2012, 23:52 #10 Super Moderator     Ghazlani M. Ali Join Date: May 2011 Location: Tokyo, Japan Posts: 1,366 Blog Entries: 23 Rep Power: 21 i'm going on a vacation on Sunday... like you said FAR may be this is easy geometry, i just need vacation... __________________ Regards, New to ICEM CFD, try this document --> https://goo.gl/NEbygB Ali

 July 11, 2012, 04:47 #11 Senior Member   AB Join Date: Sep 2009 Location: France Posts: 323 Rep Power: 14 Those kind of geometry are hard because your circle geometry meet the corner of a rectangular shape. So I think you can avoid bad elements at the intersection of those 2 shapes. I don't have much type to take a look at the geometry, will try this week :S

July 11, 2012, 05:40
#12
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AB
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Ok finally, I took some time to have a look.
Attached an example of blocking. you only need to do the association and maybe improve the position of some vertices.

You can't avoid some bad elements between the corner of your rectangle and the print of your tube, but 1/4 of O-grid help to handle it.
Attached Files
 TUBE_MANIFOLD.zip (48.0 KB, 6 views)

July 11, 2012, 06:48
#13
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lnk
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Quote:
 Originally Posted by BrolY Ok finally, I took some time to have a look. Attached an example of blocking. you only need to do the association and maybe improve the position of some vertices. You can't avoid some bad elements between the corner of your rectangle and the print of your tube, but 1/4 of O-grid help to handle it.

I tried that but I can't improve the quality because of the same reason. The quality at the attachment is the best I can do.
Attached Images
 QUALITY.jpg (56.5 KB, 19 views)
Attached Files
 work.zip (24.0 KB, 1 views)

 July 11, 2012, 07:28 #14 Senior Member   AB Join Date: Sep 2009 Location: France Posts: 323 Rep Power: 14 You can incraese the number of nodes, move the vertices in order to optmize the blocking. But you have to know that at some point, you won't be able to improve the mesh because of your geometry.

July 11, 2012, 07:41
#15
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lnk
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Quote:
 Originally Posted by BrolY You can incraese the number of nodes, move the vertices in order to optmize the blocking. But you have to know that at some point, you won't be able to improve the mesh because of your geometry.
Yes. That's the problem. I can't make all my meshes have quality over 0.5.

 July 11, 2012, 08:02 #16 Senior Member   AB Join Date: Sep 2009 Location: France Posts: 323 Rep Power: 14 Yep, but your biggest issue is not about the determinant, but about the min angle ... You can get a min determinant around 0.2, which is not that bad. But there are few cells which min angle is between 0 and 9°, which could crash your solver ... If you work hard and moving the vertices of the 1/4 of O-grid, maybe you could improve a little bit your mesh ... Or maybe someone else could provide another blocking ? Have fun

 July 11, 2012, 10:21 #17 Senior Member     Alex Join Date: Jun 2012 Location: Germany Posts: 1,266 Rep Power: 22 You have to ask yourself one question: Is it important that the geometric feature (the sharp angle) is represented by the mesh? Or wouldn't the flow field be almost exactly the same if the sharp angle is not represented by the mesh? In this case: change the geometry to allow better meshing.

 July 11, 2012, 10:30 #18 Super Moderator     Ghazlani M. Ali Join Date: May 2011 Location: Tokyo, Japan Posts: 1,366 Blog Entries: 23 Rep Power: 21 The blocking is wrong... @stief, that's exactly what i was thinking. you are right. Why do we have to follow the geometry ? how about something like this someone correct if i'm wrong... __________________ Regards, New to ICEM CFD, try this document --> https://goo.gl/NEbygB Ali

July 11, 2012, 10:59
#19
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AB
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I correct some errors in the blocking (see attached).

And I fully agree with flotus
Attached Files
 TUBE_MANIFOLD.zip (45.7 KB, 5 views)

July 11, 2012, 11:25
#20
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lnk
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Quote:
 Originally Posted by diamondx The blocking is wrong... @stief, that's exactly what i was thinking. you are right. Why do we have to follow the geometry ? how about something like this someone correct if i'm wrong...

I did in this way at the first time. It didn't work so I changed to make the mesh follow the geometry.

The pipe is not inside the cube. It goes through the cube. If the mesh doesn't follow the geometry, the mesh will have problem at the connection part too which is, I think, also difficult to correct. You can see my attachments. It is even clear at the mesh picture.

Best,
lnk
Attached Images
 QUALITY.jpg (71.3 KB, 12 views) MESH.jpg (77.8 KB, 12 views)

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