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-   -   mesh grading problem with multiple blocks (https://www.cfd-online.com/Forums/openfoam-meshing-blockmesh/83247-mesh-grading-problem-multiple-blocks.html)

aljaz December 21, 2010 03:33

mesh grading problem with multiple blocks
 
Hi!
When I'm trying to mesh a part of cylinder, made out of 3 blocks, I've found that when I try to have some grading in direction of symmetry axis, there's error message like:

--> FOAM FATAL ERROR:
face 451 area does not match neighbour 1051 by 11.4833% -- possible face ordering problem.
... etc.

With simple grading (1) everything is ok (blockMesh and checkMesh).
Interestingly though the mesh is generated and can be graded in all directions without a problem if central block is omitted (geometry of only 2 blocks - it's like a cylinder with a hole inside). The same holds true also if only the central block is meshed.
Any suggestions how can I make graded mesh on all 3 blocks?

Another question: what's the required precision when defining geometry (e.g. when using trigonometric functions)

With best regards!

P.S.: my blockMeshDict is pasted below, now it's not working, but if you replace '5' with '1' in simpleGrading specifications, it works.

FoamFile
{
version 2.0;
format ascii;
class dictionary;
object blockMeshDict;
}
// * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * //

convertToMeters 1e-4;

vertices
(
(4.6194 150 -1.91342)
(138.58193 150 -57.40251)
(5 150 0)
(150 150 0)
(4.6194 150 1.91342)
(138.58193 150 57.40251)

(4.6194 200 -1.91342)
(138.58193 200 -57.40251)
(5 200 0)
(150 200 0)
(4.6194 200 1.91342)
(138.58193 200 57.40251)

(0 150 0)
(0 200 0)
);

blocks
(
hex (0 2 3 1 6 8 9 7) (10 30 15) simpleGrading (1 10 5)
hex (2 4 5 3 8 10 11 9) (10 30 15) simpleGrading (1 10 5)
hex (12 4 2 0 13 10 8 6) (10 10 15) simpleGrading (1 1 5)
);

edges
(
arc 0 2 (4.903926 150 -0.975452)
arc 2 4 (4.903926 150 0.975452)
arc 1 3 (147.117792 150 -29.263548)
arc 3 5 (147.117792 150 29.263548)
arc 6 8 (4.903926 200 -0.975452)
arc 8 10 (4.903926 200 0.975452)
arc 7 9 (147.117792 200 -29.263548)
arc 9 11 (147.117792 200 29.263548)
);

patches
(
patch inlet
(
(6 8 9 7)
(8 10 11 9)
(6 13 10 8)
)
patch outlet
(
(0 2 3 1)
(0 12 4 2)
)
wall walls-A
(
(2 4 5 3)
)
wall walls-B
(
(1 3 9 7)
(3 5 11 9)
// (0 2 8 6)
// (2 4 10 8)
)
cyclic bf
(
(4 5 11 10)
(12 4 10 13)
(0 1 7 6)
(12 0 6 13)
)
);

mergePatchPairs
(
);


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