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Total number of faces on empty patches is not divisible by the number of cells in the

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Old   March 4, 2015, 06:49
Default Total number of faces on empty patches is not divisible by the number of cells in the
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ankit
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Hi I am new to OpenFOAM, I am trying to simulate flow over cylinder problem. But I'm facing issues in generating mesh as the above error keeps on popping (Total number of faces on empty patches is not divisible by the number of cells in the mesh. Hence this mesh is not 1D or 2D). I am pasting my blockMeshDict file, please give your valuable suggestions.

vertices
(
(-20 -25 0)
(20 -25 0)
(40 -25 0)
(-0.7071 -0.7071 0)
(0.7071 -0.7071 0)
(-0.7070 0.7071 0)
(0.7071 0.7071 0)
(-20 25 0)
(20 25 0)
(40 25 0)

(-20 -25 1)
(20 -25 1)
(40 -25 1)
(-0.7071 -0.7071 1)
(0.7071 -0.7071 1)
(-0.7071 0.7071 1)
(0.7071 0.7071 1)
(-20 25 1)
(20 25 1)
(40 25 1)
);

blocks
(
hex (0 3 5 7 10 13 15 17) (10 10 1) simpleGrading (1 1 1)
hex (1 4 3 0 11 14 13 10) (10 10 1) simpleGrading (1 1 1)
hex (4 1 8 6 14 11 18 16) (10 10 1) simpleGrading (1 1 1)
hex (6 8 7 5 16 18 17 15) (10 10 1) simpleGrading (1 1 1)
hex (1 2 9 8 11 12 19 18) (10 10 1) simpleGrading (1 1 1)
);

edges
(
);

patches
(
);

mergePatchPairs
(
);
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Old   March 6, 2015, 06:46
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Alexander Bartel
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Hi ankit,

i think you have to define the boundary like in the Users Guide (http://www.openfoam.org/docs/user/blockMesh.php).
Otherwise the faces are set as empty patches.
Empty patches are useful to define symmetry planes in case of 1D or 2D meshes.

greetings
Alex
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Old   March 11, 2015, 05:07
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ankit
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Thanks alex,

Pardon me, but is it really necessary to define boundary conditions for a mesh generation?
cause I'd watched few online tutorials and they didn't mention anything about boundary condition for mesh generation only.
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Old   March 11, 2015, 06:12
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Alexander Bartel
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You are right.
You don t need boundary conditions for the mesh generation.
But your boundary has to be defined properly.

So you have to tell OF what kind of walls or borders your mesh has, otherwise OF suggest the simplest kind of border for them all (empty as seen in your error message).

But you don t have to tell OF the values of the different fields (e.g. U, T, p ...) in the mesh, because you don t want to compute any fields yet.
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