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[GAMBIT] Problem with "link face mesh"

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Old   June 7, 2011, 04:41
Unhappy Problem with "link face mesh"
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Hi

I'm dealing with the mesh around an open rotor (propeller without duct).
As I would like to have structural mesh, I decompose the volume in the same way as the H type decomposition with the module turbo.

But here comes my problem. I linked the two faces to meet the requirement of periodic boundary types, but the mesh on the edges cannot be created correctly.

I mesh the edges a, b, c, d with a double side successive ratio 1.25 and an interval count of 80, as face 1 and face 2 are linked for mesh, there are some nodes missing at the extremity of the edge b. In the transcript window, there is a warning, saying:

WARN: Mesh copy failed for nodes on edge edge.88. You may want to use a different edge mesh evaluation type and try again.

I met the same problem when I meshed the edges in the volume A, but after I changed the order of linking, I mean linking face 3 to face 4 instead of linking face 4 to face 3, the problem was solved though I don’t know why.

Does anyone have met this problem before? Is this a bug or something? And what shall I do?

Thanks in advance for your reply and best regards.
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File Type: jpg 22222.jpg (41.1 KB, 29 views)
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File Type: jpg 44444.jpg (79.2 KB, 31 views)
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Old   June 7, 2011, 07:52
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If you change the order of linking with faces 1 and 2, do you still have the error? (as you mentionned with faces 3 and 4)
If yes, try to split edges which give you problem at location where node disppeared and try to link again. (split also opposite edge)
But I cannot answer to your question "why?"
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Old   June 10, 2011, 05:33
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thank you -mAx-

when I change the order of linking, it comes to the edge a or sometimes c and d on which there are nodes disappearing ( precisely speaking, these two or three nodes move to the end point of the edge).
I think this problem might be the result of the conflicts caused by several face links. To avoid this problem, I have deleted all the links and defined the two periodic faces as walls, and I'd like to change their types in fluent.

But when I do the make-periodic work, there comes another problem, as in TUI

/grid/modify-zones> make-periodic Periodic zone [()] 10 Shadow zone [()] 4 Rotational periodic? (if no, translational) [yes] yes Create periodic zones? [yes] yes

zone 10: matched 20 out of 3000 faces. zone 4: matched 20 out of 3000 faces.

Error: Failed to make zones periodic. Error Object: #f

while zone 10 and zone 4 are identical, both have 3000 quadrilateral wall faces.

do you have any idea about this?
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Old   June 10, 2011, 06:50
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no idea, but maybe it can help you...
periodic shadow faces
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Old   June 11, 2011, 06:30
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Hi

Have you checked the orientation of the periodic faces - i.e when you select your face and then vertex to define the face, that the direction / orientation of the face is correct?

If this is correct, I would also not mesh all 4 edges directly - i would only mesh the edges on x1 of the two periodic faces - as they are already linked, this will automatically mesh the linked edges, and also reduce the chance of your making a mistake / missing something small which may be causing the issue when you effectively mesh the two sets of edges twice.

Also (not sure if i am seeing this correctly) looks like the 'missing' node is actually on top of the final edge node as in the last graphic, the penultimate cell is formed, just highly distorted towards the corner ... maybe there is a geometry problem or something similar ...

cheers
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Old   June 21, 2011, 10:08
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thank you, max and jonathan
the problem is solved as I've found some trick. I creat the entire volume by defining a tip clearence and then the periodicity is set automatically by gambit.
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Old   June 21, 2011, 13:11
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I really need ur advice on this:
I am try to model scour under pipelines lying on a seabed using FLUENT
I intend to use eulerian multiphase model which requires me to create two zones(water and soil).
I have used projection to split a surface into two under Design modeller to create the two faces.
The issue i have is that when i try to mesh the surrounding of the cylinder with the mesher; the mesh under the pipe is scattered because of the projection line that is there.
I have attached the picture of the mesh i got
pls i will appreciate any contribution
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