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-   -   Meshing a circle (http://www.cfd-online.com/Forums/openfoam-meshing-blockmesh/61798-meshing-circle.html)

 sega May 13, 2008 11:24

Hello World. I thought abou

Hello World.

Unfortunately it contains some stretched elements.

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

http://www.cfd-online.com/OpenFOAM_D...your_image.gif

 sega May 13, 2008 11:25

Sorry, there was a problem wit

Sorry, there was a problem with the upload.

http://www.cfd-online.com/OpenFOAM_D...ges/1/7661.png

 ngj May 13, 2008 12:05

Hi Sebastian I have come to

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,

Niels

 eugene May 13, 2008 12:43

What we used to do, is to put

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.

 cedric_duprat May 13, 2008 13:08

Hi Sebastian, I think you w

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

 sega May 14, 2008 02:56

Now I get it. You mean someht

Now I get it.
You mean somehting like that:

http://www.cfd-online.com/OpenFOAM_D...ges/1/7669.png

 eugene May 14, 2008 03:57

Exactly. I know its not ideal,

Exactly. I know its not ideal, especially at the 3 block junction, but I think it is the best compromise given the available resources.

 sega May 23, 2008 11:06

Hey. Me again. So, I did it

Hey. Me again.

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

http://www.cfd-online.com/OpenFOAM_D...your_image.gif

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!

 sega May 23, 2008 11:13

Sorry, the Image was too large

Sorry, the Image was too large.

http://therealsega.th.funpic.de/openfoam/mesh.png

 santos May 24, 2008 06:15

Hello, Theres a face missin

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.

Regards,
Jose Santos

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