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Old   July 9, 2012, 14:50
Question Why don't we use domain interface to solve this problem?
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lnk
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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
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File Type: jpg O-grid.jpg (19.5 KB, 38 views)
File Type: jpg block.jpg (53.8 KB, 47 views)

Last edited by lnk; July 18, 2012 at 15:35.
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Old   July 9, 2012, 15:14
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what u want to do?
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Old   July 9, 2012, 15:49
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A=B. So it does not make any difference.
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Old   July 9, 2012, 16:20
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Quote:
Originally Posted by Far View Post
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
File Type: jpg block.jpg (53.0 KB, 26 views)
File Type: jpg quality.jpg (51.3 KB, 29 views)
File Type: jpg surface.jpg (50.8 KB, 32 views)
File Type: jpg mesh.jpg (60.9 KB, 31 views)
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Old   July 10, 2012, 02:31
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This is easy case for ICEM Hexa. If you can share your files, we can give a quick try.
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Old   July 10, 2012, 04:38
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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 !
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Old   July 10, 2012, 06:30
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Quote:
Originally Posted by Far View Post
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
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File Type: zip abc.zip (53.9 KB, 5 views)

Last edited by lnk; July 11, 2012 at 05:15.
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Old   July 10, 2012, 08:10
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Quote:
Originally Posted by BrolY View Post
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?
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Old   July 10, 2012, 23:50
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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...
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Old   July 10, 2012, 23:52
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i'm going on a vacation on Sunday... like you said FAR may be this is easy geometry, i just need vacation...
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Old   July 11, 2012, 04:47
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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
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Old   July 11, 2012, 05:40
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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.
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File Type: zip TUBE_MANIFOLD.zip (48.0 KB, 6 views)
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Old   July 11, 2012, 06:48
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Quote:
Originally Posted by BrolY View Post
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.
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File Type: jpg QUALITY.jpg (56.5 KB, 19 views)
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File Type: zip work.zip (24.0 KB, 1 views)
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Old   July 11, 2012, 07:28
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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.
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Old   July 11, 2012, 07:41
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Quote:
Originally Posted by BrolY View Post
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.
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Old   July 11, 2012, 08:02
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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
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Old   July 11, 2012, 10:21
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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.
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Old   July 11, 2012, 10:30
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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...
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Old   July 11, 2012, 10:59
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I correct some errors in the blocking (see attached).

And I fully agree with flotus
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Old   July 11, 2012, 11:25
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Quote:
Originally Posted by diamondx View Post
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,
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Attached Images
File Type: jpg QUALITY.jpg (71.3 KB, 12 views)
File Type: jpg MESH.jpg (77.8 KB, 12 views)
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