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Old   July 13, 2010, 14:20
Default Overlapping elements
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Hi everyone,

Thanks for reading my post!
I am analysing an unconventional airfoil with a sharp leading and trailing edge. The airfoil is also very thin. For this I am using a fully structured mesh.
Although the quality of the mesh is satisfying, I have some overlapping elements at the trailing edge. Actually all the elements along the trailing edge of the upper and lower surface overlap. Due to this the fluent won't load the mesh so the problem must be solved.
I cannot change the geometry of the airfoil so I have to find a way around to resolve this problem but so far without succes.

In the figures you can see the elements that overlap. Note that only these are shown. I know the aspect ratio is off but these pictures only serve as an illustration.

Does anyone has a suggestion on how to solve the problem of the overlapping elements? Or how to prevent this? Preferrably without changing the spacings or the surrounding mesh and keeping the structured mesh?
The standard fix function does not work...

The face(s) of the surrounding block(s) is projected on the surfaces.

Any help will be greatly appreciated since the problem is urgent . Well anyway thanks for reading the post and I hope you can help me out.
Attached Images
File Type: jpg airfoil.jpg (80.4 KB, 89 views)
File Type: jpg TE_zoom.jpg (78.6 KB, 73 views)
File Type: jpg TE_zoom2.jpg (75.6 KB, 56 views)
File Type: jpg TE_zoom3.jpg (79.6 KB, 51 views)
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Old   July 13, 2010, 15:07
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hi,

Ok I solved the problem. The fix function will still not work, remeshing was not an option thus.
I played around with some of the other repair mesh tools without any satisfying result.
However the mesh is not rejected by fluent due to the overlapping elements I learned.It was a memory issue instead.
If anyone still has a hint on how to remove the overlapping elements I would love to know.

Thanks again
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Old   July 15, 2010, 22:01
Cool Not a Problem.
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Overlapping elements is only a "Possible Problem" and not an "Error" under Check Mesh.

They are not always avoidable and they are not always bad.

In this case, you have overlapping geometry, so there is no way to avoid these. Fortunately, they shouldn't be a problem because you have already generated mesh around the overlapping elements and are not trying to generate tetra mesh within the gap.

if you planed to use a method like "Delaunay" within the tight region there could be a problem. Usually, this is really a problem for triangle mesh when the user wants to generate a delaunay mesh but the third points don't line up nicely (like they do here). Any Tetra elements that would be created would have a very poor quality.

It is also a useful check because it may find areas where the mesh is folding back on its self. This could indicate other problems, such as bad geometry, which would be good to know if you didn't expect these sorts of overlapping regions.

For a Hexa mesh where you are looking at thin section like this, you don't even need to run this check.

Simon
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Old   July 19, 2010, 09:18
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Hi Simon,

Thanks for the information which as usual makes all more clear

Still want to post the private conversation we had on scripting and reference blocking a while ago but lost the messages I sended to you... Do you still have a copy in your inbox? If so can you send them to me so I can post the conversation?

Thanks again!
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Old   July 19, 2010, 09:59
Default Sorry.
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I just did a quick search thru my email and found three conversations to your gmail address, but none on this topic... Perhaps I deleted it on my end also.
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Old   December 29, 2012, 11:01
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hi i am designing the helical coil heat exchanger..i want to helical coil in a cylinder body..i want to get overlapping mesh of helical coil surface ..how i do that in ansys 13
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