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Meshing a circle

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Old   May 13, 2008, 11:24
Default Hello World. I thought abou
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Sebastian Gatzka
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Hello World.

I thought about this solution to create a spherical mesh.
Unfortunately it contains some stretched elements.

Do you think this is the best of maybe the only way of creating a spherical grid?


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Old   May 13, 2008, 11:25
Default Sorry, there was a problem wit
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Sorry, there was a problem with the upload.


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Old   May 13, 2008, 12:05
Default Hi Sebastian I have come to
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Hi Sebastian

I have come to think about it, and if you make a block with "corners" in 45, 135, 225 and 315 degrees and make arcs which connects to 0, 90, 180 and 270 degrees, then you will get a perfect circle.

Best regards,

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Old   May 13, 2008, 12:43
Default What we used to do, is to put
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What we used to do, is to put all the block points except the one on the axis on the same radius from the axis. There is still some distortion, but less than what you have.

I.e. if the square block is defined by

2----3
|......|
|......|
0----1

And the coordinates are

p0 = (0, 0, 0)
p1 = (1, 0, 0)
p2 = (0, 1, 0)

Then

p3 = (sqrt(0.5), sqrt(0.5), 0)

not

p3 = (1, 1, 0)

like you have it.
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Old   May 13, 2008, 13:08
Default Hi Sebastian, I think you w
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Hi Sebastian,

I think you will find what you are looking for here :
http://openfoamwiki.net/index.php/Si...e_next_meeting

there, you will find an sourceForge adress where all the cases are avaiable. (http://openfoam-extend.svn.sourceforge.net/svnroot/openfoam-extend/trunk/Breeder /OSIG/TurboMachinery/ercoftacConicalDiffuser)
These are not just pipes but, you can modify (m4 files) the mesh file easily to get what you want.
there are lot of parameters avaiable to make your own mesh.

I hope it will be helpfull

Cedric
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Old   May 14, 2008, 02:56
Default Now I get it. You mean someht
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Now I get it.
You mean somehting like that:


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Old   May 14, 2008, 03:57
Default Exactly. I know its not ideal,
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Exactly. I know its not ideal, especially at the 3 block junction, but I think it is the best compromise given the available resources.
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Old   May 23, 2008, 11:06
Default Hey. Me again. So, I did it
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Hey. Me again.

So, I did it and created a circular mesh out of about 20 hex-blocks:



The problem is, that when I'm trying to solve my problem on this grid I get this message:

--> FOAM FATAL ERROR : This mesh contains patches of type empty but is not 1D or 2D
by virtue of the fact that the number of faces of this
empty patch is not divisible by the number of cells.


I'm not sure what to think, but is this because of the internal faces connecting the blocks?
I read the User Guide about Miltiple Blocks but I'm not sure I understood it. Maybe I'm not, because I don't know if my problem has something to do with this...

If you want to have a look:
http://therealsega.th.funpic.de/open...ourMesh.tar.gz

Thanks so far!
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Old   May 23, 2008, 11:13
Default Sorry, the Image was too large
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Sorry, the Image was too large.

http://therealsega.th.funpic.de/openfoam/mesh.png
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Old   May 24, 2008, 06:15
Default Hello, Theres a face missin
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Hello,

Theres a face missing in your patch fixedWalls. Open your case in Paraview, and you'll see that there is a face at the top that is not included in fixedWalls, rather in defaultFaces.

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