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Old   November 13, 2014, 02:57
Default getting unwanted internal faces
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Arjun
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Dear all,

I am new to blockMesh utility. I have attached my domain with corresponding vertices numbering. I want to divide my domain in to four as marked in the figure.
for that following codes are used:

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

But i am getting two internal face, its orientation is (7 17 9 19) and (9 19 3 13)

I want to get rid of this internal face. Or help me with any other condition that will nullify the effect of internal face.
DSC_1749.jpg

Last edited by Arjun Jayakumar; November 13, 2014 at 04:52.
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Old   November 13, 2014, 05:19
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Tushar Chourushi
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Quote:
Originally Posted by Arjun Jayakumar View Post
Dear all,

I am new to blockMesh utility. I have attached my domain with corresponding vertices numbering. I want to divide my domain in to four as marked in the figure.
for that following codes are used:

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

But i am getting two internal face, its orientation is (7 17 9 19) and (9 19 3 13)

I want to get rid of this internal face. Or help me with any other condition that will nullify the effect of internal face.
Attachment 35071
I would rather create blocks out of nodes (9,19) and divide block 0 and 1, similar to block 2 and 3.

Anyways, try defining your Boundary Conditions like this,

defaultFaces
{
type empty;
}

Re-run your case, I hope it will solve your problem.

-
Best Luck!
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Old   November 13, 2014, 06:02
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Quote:
Originally Posted by Tushar@cfd View Post
I would rather create blocks out of nodes (9,19) and divide block 0 and 1, similar to block 2 and 3.

Anyways, try defining your Boundary Conditions like this,

defaultFaces
{
type empty;
}

Re-run your case, I hope it will solve your problem.

-
Best Luck!
dear tushar,

thank you for your time.
I have already tried this by setting the defaultfaces to empty but this will not help to solve the problem.
Its showing higher velocities at the patch surface, which result in too high courant number.
Do you know how i am getting these internal faces, without defining any where in the blockMesh dictionary.
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Old   November 13, 2014, 06:34
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Quote:
Originally Posted by Arjun Jayakumar View Post
dear tushar,

thank you for your time.
I have already tried this by setting the defaultfaces to empty but this will not help to solve the problem.
Its showing higher velocities at the patch surface, which result in too high courant number.
Do you know how i am getting these internal faces, without defining any where in the blockMesh dictionary.
Dear Arjun,

The error is in the blockMesh, due to node (9, 19) which is connected to a face. If you remove this node and use only 3 blocks it will work, as it will follows the block rule.

If your case demands such mesh only. Then, you can try "merge" option of OpenFOAM. Although, I never tried it but I think that will help you resolve.

Please, do share to FOAM community if you happen to get correct solutions.

-
Best Luck!
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Old   November 13, 2014, 07:36
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Quote:
Originally Posted by Tushar@cfd View Post
Dear Arjun,

The error is in the blockMesh, due to node (9, 19) which is connected to a face. If you remove this node and use only 3 blocks it will work, as it will follows the block rule.

If your case demands such mesh only. Then, you can try "merge" option of OpenFOAM. Although, I never tried it but I think that will help you resolve.

Please, do share to FOAM community if you happen to get correct solutions.

-
Best Luck!
dear tushar,

I need to define a patch on face (4 14 15 5).

If i try with 3 blocks it will lead to error "face 0 in patch 0 does not have neighbour cell face: 4(4 14 15 5).

I am not familiar with merge. which all faces do you suggest to merge.

Thank you
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Old   November 13, 2014, 08:20
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Quote:
Originally Posted by Arjun Jayakumar View Post
dear tushar,

I need to define a patch on face (4 14 15 5).

If i try with 3 blocks it will lead to error "face 0 in patch 0 does not have neighbour cell face: 4(4 14 15 5).

I am not familiar with merge. which all faces do you suggest to merge.

Thank you
Dear Arjun,

You can easily construct 3 block for the case which you have referred in the figure. Follow carefully the blockMesh strategy of OpenFOAM, refer link below for the same:

http://www.openfoam.org/docs/user/blockMesh.php

For merge patch I am not an expert. You can explore it.

-
Best Luck!
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Old   November 13, 2014, 15:03
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An alternative method is to generate the 3-block mesh which works, then use topoSet to select the faces that correspond to face 4 14 15 5 and use createPatch to generate the boundary patch.

I've found this approach is more consistent and allows you to make all kinds of boundary patches that only partially cover the domain boundaries, and requires less debugging of the blockMesh dict file which can become a real headache.
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Old   November 14, 2014, 07:48
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Quote:
Originally Posted by mturcios777 View Post
An alternative method is to generate the 3-block mesh which works, then use topoSet to select the faces that correspond to face 4 14 15 5 and use createPatch to generate the boundary patch.

I've found this approach is more consistent and allows you to make all kinds of boundary patches that only partially cover the domain boundaries, and requires less debugging of the blockMesh dict file which can become a real headache.
Thank you for your suggestion Marco. I think it will take some time for me to familiarize with topoSet utility. Will post the updates and looking forward to your help in future.
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