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-   -   [blockMesh] Meshes made of several blocks (https://www.cfd-online.com/Forums/openfoam-meshing/151356-meshes-made-several-blocks.html)

zaphod April 9, 2015 04:51
Meshes made of several blocks
 
Hi!

I am trying to make a mesh made of several blocks in order to have a geometry containing obstacles but I keep obtaining error messages about faces that don't have neighbour cell faces.

I can reproduce the problem by trying to make a mesh made of 2 blocks inside a cube.

In blockMeshDict, I create a cube and I add 4 points in the middle, along the y axis, to slice it in half.
Quote:
vertices
(
( 0 0 0)
(10 0 0)
(10 10 0)
( 0 10 0)
( 0 0 10)
(10 0 10)
(10 10 10)
( 0 10 10)

( 0 5 0)
( 0 10 0)
(10 5 0)
(10 5 10)
);
Then I attempt to make 2 blocks.
Quote:
blocks
(
hex ( 0 8 9 4 1 10 11 5) (10 5 10) simpleGrading (1 1 1)
hex ( 3 7 9 8 2 6 11 10) (10 5 10) simpleGrading (1 1 1)
);
But I keep obtaining the following error message.
Quote:
--> FOAM FATAL ERROR:
face 0 in patch 0 does not have neighbour cell face: 4(0 3 2 1)
What am I doing wrong?

Thank you!

Cheers,

Philippe

alexeym April 9, 2015 05:05
Hi,

In general the error means you have messed up definition of patches (boundary section). Can you post your whole blockMeshDict as an attachment?

zaphod April 9, 2015 05:09
Hello!

Thank you for your reply.

Here is the boundary section.

Quote:
boundary
(
walls
{
type wall;
faces
(
(0 3 2 1)
(0 1 5 4)
(1 2 6 5)
(2 3 7 6)
(0 4 7 3)
(4 5 6 7)
);
}
);
Should the boundaries be cut in the same way as the cube? I had thought it was independent. I am going to try.

Cheers,

Philippe

alexeym April 9, 2015 05:18
Hi,

Patches in general composed of boundaries of the blocks. If you cut cube, you cut boundaries. So what was described before cutting as a single face should be described as several faces.

zaphod April 9, 2015 05:42
I have sliced the boundaries in 2.

Quote:
boundary
(
walls
{
type wall;
faces
(
( 0 4 9 8)
( 1 10 11 5)
( 3 8 9 7)
( 2 6 11 10)
( 0 8 10 1)
( 4 5 11 9)
( 2 10 8 3)
( 6 7 9 11)
( 0 1 5 4)
( 3 7 6 2)
);
}
);
But, now, I obtain the following error message:
Quote:
--> FOAM FATAL ERROR:
Inconsistent number of faces between block pair 0 and 1
However, t seems to me that there is the same number of cells on both sides of the slice.

Thanks.

Philippe

alexeym April 9, 2015 06:58
Hi,

Start with visualizing your blocks, to check if you have made mistake there. I.e. you comment out patches definitions, run blockMesh, open mesh in paraview. Your vertices look rather suspicious, among four additional points for some reason ( 0 10 0) appeared. Also I am not quite sure in correctness of your vertices numbering in blocks definitions.

I can try to reconstruct the case from the pieces you have posted and try to look for error but I would rather wait till you post archive with the case files.


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