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[blockMesh] emove a cylinder from a cube

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Old   May 29, 2016, 10:03
Default emove a cylinder from a cube
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A. Min
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Hi
I want to simulate Free Convection flow of water over a circular cylinder as a practice.
How can I remove a cylinder from a cube?

Thanks friends
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Old   May 29, 2016, 16:57
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Marco Atzori
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Hi!

I'm not sure it is what you are looking for: try to use blockMesh with the attachment (I changed a little bit what I found in this post: http://www.cfd-online.com/Forums/ope...-cylinder.html)

Anyway, if I had to started from scratch, I would use Salome to obtain an .stl and Snappy or cfMesh for the mesh.

Cheers!
Attached Files
File Type: txt blockMeshDict.txt (5.5 KB, 22 views)
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Old   May 30, 2016, 02:36
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Quote:
Originally Posted by Atzori View Post
Hi!

I'm not sure it is what you are looking for: try to use blockMesh with the attachment (I changed a little bit what I found in this post: http://www.cfd-online.com/Forums/ope...-cylinder.html)

Anyway, if I had to started from scratch, I would use Salome to obtain an .stl and Snappy or cfMesh for the mesh.

Cheers!
Hi Marco
Thanks a lot for your cooperation!
It works well and I can see the Mesh.
I'm a beginner in openFoam. I know about Verticies, blocks, edges but not about patches! What are patches? in fact why do we use patch command in blockMeshDict?
In addition, could you please explain how to create this mesh by that code?

Thanks a lot
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Old   May 30, 2016, 03:04
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Hi,

Patches are basically faces on which usually boundary conditions are applied for the problem that you are solving. It is the generic term for faces on which BCs will be applied.

While patch is the generic term, there are instance when you might want to be more specific about the type of patch the face is, e.g. wall, symmetry etc.

You can read more about it here (under the section on boundary): http://cfd.direct/openfoam/user-guide/blockMesh/

Hope this helps.

Cheers,
Antimony
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Old   May 30, 2016, 03:19
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Hi Antimony!!
of course it was helpful. but in the page you introduce me, there is a code that has boundary, not patches:


boundary // keyword
(
inlet // patch name
{
type patch; // patch type for patch 0
faces
(
(0 4 7 3) // block face in this patch
);
} // end of 0th patch definition
outlet // patch name
{
type patch; // patch type for patch 1
faces
(
(1 2 6 5)
);
}
walls
{
type wall;
faces
(
(0 1 5 4)
(0 3 2 1)
(3 7 6 2)
(4 5 6 7)
);
}
);


while, in the code that is sent to me by my friend Marco Atzori (top of this page) we have patches instead of boundaries!

patches
(
symmetryPlane down
(
(42 43 56 55)
(41 42 55 54)
(43 50 63 56)
(50 49 62 63)
)
patch right
(
(2 3 22 21)
(3 6 25 22)
(2 38 51 21)
(38 41 54 51)
)
symmetryPlane up
(
(7 8 27 26)
(6 7 26 25)
(8 18 37 27)
(18 17 36 37)
)
patch left
(
(14 13 32 33)
(17 14 33 36)
(46 13 32 59)
(49 46 59 62)
)
symmetryPlane cylinder
(
(10 5 24 29)
(5 0 19 24)
(16 10 29 35)
(11 16 35 30)
(45 40 53 58)
(40 0 19 53)
(48 45 58 61)
(11 48 61 30)
)
);


why?
whats difference?


Thanks my dear friend
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Old   May 30, 2016, 04:49
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Hi,

I don't think there is a difference. I think "patches" at that location is from an older version of OF, while "boundary" is the one that has been around from OF 2.1.x (at least that is how long I can remember it being there). The one sent by Atzori seems to be from OF 1.5, though I could be wrong about that.

Cheers,
Antimony
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Old   May 30, 2016, 04:55
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Marco Atzori
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Hi!
Antimony's perfectly right: I took the example directly from the previous post and it is an old version: I suppose that a sort of partial redundancy is adopted because I managed to compile the attachment in OF 2.2 (the attachment, what you have post later differs from the presence of the “symmetryPlane”), but I recognise now the difference with the current standard: I’m writing a new dict, just one sec: I notice that “front” and “back” are not included in the boundary and it takes some min to add them
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Old   May 30, 2016, 05:14
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Hi!

It is better now

Notice that the "empty type" is mandatory in that case for frontAndBack since it is a 2D case.

Cheers!
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File Type: txt blockMeshDict.txt (6.4 KB, 7 views)
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Old   May 30, 2016, 09:27
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Thanks dear friends. You helped me a lot!

Best Regards...
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