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[ICEM] ICEM changes geometry

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Old   June 15, 2012, 21:07
Default ICEM changes geometry
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hello everyone,

im working at my dissertation for a couple of months, in simulating a pipe flow in four different pipe systems with a diameter of 16mm. the main features are a straight pipe, a 90 degree curve of the pipe, a 90 degree edge and a T-shaped branching.
i planned to use ansys geometry, ansys mesh and fluent, but since the meshing tool couldnt handle more than 4 million elements, i changed to icem for meshing my geometry.
i created a geometry with all the main features, for a mesh independency study ( not sure if its called this way in english). (1st picture)

now my problem is, that icem seems to change the surface behind the branching. one of the straight lines, describing the surface, seems to warp around the pipe, and is messing up my associations to the surface (2nd picture)

i would be really thankful if somebody had an idea what i am doing wrong and how to fix the problem.

marius
Attached Images
File Type: jpg Geometry Netzunabhängigkeitsanalyse.JPG (30.4 KB, 27 views)
File Type: jpg Geometry messed up surface.JPG (17.9 KB, 28 views)
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Old   June 16, 2012, 14:05
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Hi, are u sure your geometry has changed? (I guess your blocking is changed)
try associate all edges and vertices. you can also check association by right click on the Edge and Show Association.
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Old   June 16, 2012, 22:45
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hi, i am quite sure, that its not the blocking, that changes, but the geometry.
the first picture shows the blocks of my modell. the second shows the associations in the inlet. i associated the outer surfaces of my ogrid to the wall. i did the same associations behind my branching (third pic). there you can see, that the arrow is not pointing to the closest wall, but to the warped line, and so messes up the associations. the fourth pic shows the pre mesh.

hope someone has any idea how to fix my problem
Attached Images
File Type: jpg blocking.JPG (42.8 KB, 11 views)
File Type: jpg associations inlet.JPG (51.8 KB, 11 views)
File Type: jpg associations branching.JPG (72.4 KB, 15 views)
File Type: jpg pre mesh.jpg (72.3 KB, 21 views)
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Old   June 17, 2012, 17:39
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although it is hard to imagine your 3d views, my experience says in such a pre-mesh there exist wrong association as you mentioned.
my question is, how you associate square edges (4 edges) to the round geometry? I myself select four edges together and then I select whole round curve.

I also recommend to split square edges with Edit Edge and then split Edge and Linear. if you do that, when you move the splitting vertex, it should automatically bind to the round curve.
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Old   June 17, 2012, 18:04
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I forgot to say that since your edeg color is black, i think it means that your curve is associated to the surface (not a curve). (you can verify that by going to ICEM user guide to see what black edge means.)
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Old   June 18, 2012, 03:58
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You only need to associate curves to edges.
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Old   June 18, 2012, 05:21
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yes, the associations seem to be the reason for the problem. i thought the face to surface association would be best, since i want to have my mesh projection all the way through the pipe.
now i tried the edge to curve association. i associated the four outer edges of the inlet and outlets to the curves describing the pipe profile.
the pre mesh than looked very good (pic 1 and 2) but after saving and opening the project again, the surface again warped around my pipe.
i noticed that there are some default associations in the branch ( pic 3),
could they cause the problems? they are white colored, and the icem documentation says, that its an association between two material volumes. i am not sure what that means in specific.
and is it enough to associate only the edges at the inlet and outlet, even for a more complex pipe system as shown in the fourth picture?

thank you already for your answers and fast replies
Attached Images
File Type: jpg pre mesh edge association before saving.jpg (61.4 KB, 19 views)
File Type: jpg pre mesh edge association before saving2.JPG (79.1 KB, 19 views)
File Type: jpg default associations.JPG (55.7 KB, 16 views)
File Type: jpg Geometry Netzunabhängigkeitsanalyse.JPG (30.4 KB, 15 views)
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Old   June 18, 2012, 09:37
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Again, it looks like an association issue.
Post the *.tin and *.blk files.
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Old   June 18, 2012, 14:32
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i couldnt solve the problem yet, but here are the .tin and .blk files
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File Type: zip branching.zip (8.0 KB, 7 views)
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Old   June 18, 2012, 17:58
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i noticed, that the geometry i uploaded, is already with the warped line. here is the .tin file, how the geometry is supposed to be
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File Type: zip Geom.zip (4.2 KB, 4 views)
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Old   June 19, 2012, 04:24
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It looks like your "tin" file is wrong. The first time I imported it, it worked well.
When I saved it as a project, and re-opened the project, the surface went wrong ...
I think you should send your "tin" file to the support and ask them how to fix this issue !
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Old   June 19, 2012, 10:33
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I tried and fixed your tin geometry everything should work fine now.
See attached file below. let me know if it works
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File Type: zip branching.zip (30.0 KB, 2 views)
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New to ICEM CFD, try this document --> http://goo.gl/G2gkE
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Old   June 20, 2012, 06:09
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thanks a lot, for your attempt, the project you created works fine.

since this was only a test geometry and i have 5 more to mesh, i tried to track your preceed and to redo what you did, but i didnt have sucess yet.

first i added some points and curves a long the branching and the circle right in the branchin, just as you did.
than i created a new part including these points and curves and the pipe surface behind the branching. at this point i already realized, that after saving and reopening, the surface is curved again.
further i noticed, that you applied edge to curve association at the inlet and outlets, and two more in the branching.

could you tell me if i miss something or why my attempts still dont work?

thanks a lot in advance

marius
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Old   June 20, 2012, 07:47
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You have to redo the surfaces from the curves.
The issue comes from the surface, not from the blocking.

It could be interesting to send your model to the support to have an idea why your surfaces look good the 1st time and go wrong the next time you open the project.
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Old   June 20, 2012, 08:52
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your blocking was good. i didn't touch it. i just added some associations.
The main problem was the surfaces, i deleted the surfaces and created new ones, using the "curve driven" feature under "create surface" in "geometry" then i trimmed the surface using curve at the intersection.
The reason why your geometry go wrong with the imported one is unknown, it's weird. As BrolY said send it to the support team whenever you get free time they can help you investigate the problem
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