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-   -   2D axissym mesh problem (http://www.cfd-online.com/Forums/openfoam-solving/60011-2d-axissym-mesh-problem.html)

 chris1980 August 7, 2006 18:02

I want to create a 2D axis-sym

I want to create a 2D axis-sym mesh:

I have used the following blockMeshDict
vertices
(
(0 0 0)
(44.956 -1.963 0)
(44.956 1.963 0)
(0 0 90)
(44.956 -1.963 90)
(44.956 1.963 90)
);

blocks
(
hex (0 1 2 0 3 4 5 3) (20 1 20) simpleGrading (1 1 1)
);

edges
(
arc 1 2 (45 0 0)
arc 4 5 (45 0 90)
);

patches
...

But when I run checkMesh, the util complains about highly skewed cells!

--> FOAM Warning :
From function primitiveMesh::checkFaceSkewness(const bool report, labelHashSet* setPtr) const
in file meshes/primitiveMesh/primitiveMeshCheck.C at line 834
Large face skewness detected. Max skewness = 284.634 percent.
This may impair the quality of the result.
40 highly skew faces detected.
Writing 40 skew faces to set skewFaces

What is wrong with my mesh. Is there something what I can do to get rid of the bad skewness???

 chris1980 September 15, 2006 08:40

Can nobody comment my mesh pro

Can nobody comment my mesh problem?

 mattijs September 15, 2006 12:01

checkMesh says that there is s

checkMesh says that there is skewness for boundary faces. If you check you'll see that all your wedge faces are skew, i.e. the face centre is not the normal projection of the cell centre. Make the skew angle larger and you'll see where the error comes from.

 chris1980 September 15, 2006 12:16

Thanks Mattijs, so the prob

Thanks Mattijs,

so the problem with highly skewed cells is unavoidable with a "wedge" geomertry right? Please correct me if I am wrong.

If not, how to do a better wedge mesh?

 chris1980 September 17, 2006 13:06

Ok the faces which checkMesh c

Ok the faces which checkMesh complains belong to cells which are aligned along the axis of my wedge.

So I was wondering if someone is able to tell me how to create a wedge without skewed faces? See my first message this is the way I am creating the wedge at the moment.

 hjasak September 17, 2006 13:32

I suspect what bothers you are

I suspect what bothers you are the faces on the front and back surface of the wedge - you can safely ignore the message there. If you wish, you can remove zero-area faces on the axis itself, simply be creating only one set of axis points and using duplicates in block definition.

Enjoy,

Hrv

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