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face normal direction of a wedge

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Old   July 15, 2015, 19:51
Default face normal direction of a wedge
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I tried to create a wedge for a axial symmetrical problem. This figure is the geometry. Following is my
blockMeshDict file.

According to the user guide, the normal direction of any boundary face should point to outside of the computational zone. So I defined all the faces in this way. Error messages popped out when I run blockMesh, saying outlet and axi_symm-r don't have neighbor cell faces.

I found that if I change the vertices in the reversed order (the quoted lines) I can generate the mesh successfully. But in this case, the normal directions of these two faces are actually pointing into the computational zone. I wonder what is wrong. Thanks

convertToMeters 1;

vertices
(
(0 0 0) //0
(8 0 0) //1
(0 -0.0034905 0.099985) //2
(8 -0.0034905 0.099985) //3
(8 0.0034905 0.099985) //4
(0 0.0034905 0.099985) //5
);

blocks
(
hex (0 1 1 0 2 3 4 5) (100 1 20)
simpleGrading
(
1
1
(
(0.5 0.5 4)
(0.5 0.5 0.25)
)
)

);

edges
(
arc 2 5 (0 0 0.1)
arc 3 4 (8 0 0.1)
);

patches
(
patch
inlet
(
(0 2 5 0)
)

patch
outlet
(
// (1 3 4 1)
(1 4 3 1)
)

wedge
axi_symm-f
(
(0 1 3 2)
)

wedge
axi_symm-r
(
// (0 1 4 5)
(0 5 4 1)
)

wall
wall
(
(2 3 4 5)
)
);

mergePatchPairs
(
);

// ************************************************** *********************** //
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Old   July 16, 2015, 04:48
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Alexander Bartel
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Hi popo, or kaka or whatever (I hope you aren't german )

You made an fault by defining your block.
If you want to let collapse some points to create a prism... don't let the first 4 collapse, as they are used to define your local coordinate system of the block.

I hope it helps
regards
Alex
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Old   July 16, 2015, 13:39
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Thanks for the response.

I changed the geometry. So now it is like:


Code:
/*--------------------------------*- C++ -*----------------------------------*\
| =========                 |                                                 |
| \\      /  F ield         | OpenFOAM: The Open Source CFD Toolbox           |
|  \\    /   O peration     | Version:  2.4.0                                 |
|   \\  /    A nd           | Web:      www.OpenFOAM.org                      |
|    \\/     M anipulation  |                                                 |
\*---------------------------------------------------------------------------*/
 FoamFile
 {
     version     2.0;
     format      ascii;
     class       dictionary;
     object      blockMeshDict;
 }
 // * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * //
 
 convertToMeters 0.01;
 
 vertices        
 (
     (-0.008026884 0 -1)             //0
     (0.008026884 0 -1)           //1
     (0.008026884 8.8 -1)             //2
     (-0.008026884 8.8 -1)               //3
     (0 0 0)              //4
     (0 8.8 0)            //5
 );
 
 blocks          
 (
         hex (0 1 2 3 4 5 5 4) (1 100 20) 
         simpleGrading 
         (
             1
             1 
             (
                (0.5 0.5 4)
                (0.5 0.5 0.25)
             )             
         )
 
 );
 
 edges           
 (
 );
 
 patches         
 (
         patch
         inlet 
         (
                 (4 0 1 4)
         )
 
         patch
         outlet
         (
                 (2 3 5 5)
         )
 
         wedge
         axi_symm-f
         (
                 (1 2 5 4)
         )
 
         wedge
         axi_symm-r
         (
                 (0 4 5 3)
         )
                 
         wall
         wall
         (
                 (0 3 2 1)
         )
 );
 
 mergePatchPairs
 (
 );
 
 // ************************************************************************* //
However, I still had the same error message:
--> FOAM FATAL ERROR:
face 0 in patch 0 does not have neighbour cell face: 4(4 0 1 4)


Quote:
Originally Posted by alexB View Post
Hi popo, or kaka or whatever (I hope you aren't german )

You made an fault by defining your block.
If you want to let collapse some points to create a prism... don't let the first 4 collapse, as they are used to define your local coordinate system of the block.

I hope it helps
regards
Alex
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Old   July 16, 2015, 14:39
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I didn't find it in the user guide. But does the symmetrical axis need to be one of the coordinate axis?

thanks

Quote:
Originally Posted by alexB View Post
Hi popo, or kaka or whatever (I hope you aren't german )

You made an fault by defining your block.
If you want to let collapse some points to create a prism... don't let the first 4 collapse, as they are used to define your local coordinate system of the block.

I hope it helps
regards
Alex
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Old   July 16, 2015, 17:23
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Alexander Bartel
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hmmm, looks good so far...

but I am not sure about your multi-grading-thing... never done that... I hope you are sure that there is no error.

Furthermore I always rather describe the boundary than the patches.
like here http://cfd.direct/openfoam/user-guide/blockmesh/ see under 5.3.1.5 The boundary

I hope it helps

Edit:
Another possible error could be that you haven't defined the empty patch (4 5 5 4) . But I don't know it refers to the error message.
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Old   July 17, 2015, 10:45
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I found this example:
https://openfoamwiki.net/index.php/M...s/AxiSymmetric

But even in this case, the normal direction of the outlet is pointing to the computational domain. I am really confused...

Quote:
Originally Posted by alexB View Post
hmmm, looks good so far...

but I am not sure about your multi-grading-thing... never done that... I hope you are sure that there is no error.

Furthermore I always rather describe the boundary than the patches.
like here http://cfd.direct/openfoam/user-guide/blockmesh/ see under 5.3.1.5 The boundary

I hope it helps

Edit:
Another possible error could be that you haven't defined the empty patch (4 5 5 4) . But I don't know it refers to the error message.
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Old   July 17, 2015, 15:47
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Alexander Bartel
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the rule to set the boundary is defined in the users guide as
Quote:
The order in which the vertices are given must be such that, looking from inside the block and starting with any vertex, the face must be traversed in a clockwise direction to define the other vertices
but I thought it fits to your dict
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Old   July 17, 2015, 16:30
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yeah, in my case, it fits. But the case doesn't work.

All the working cases I saw so far have one or two faces violating this rule. I am really confused...

Quote:
Originally Posted by alexB View Post
the rule to set the boundary is defined in the users guide as

but I thought it fits to your dict
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Old   July 19, 2015, 13:13
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Alexander Bartel
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sorry, but I am at my wits end.

Have you defined the empty face?
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Old   July 20, 2015, 11:29
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I tried that as well.

Thanks for your help anyway
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Old   July 20, 2015, 15:44
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there is no try... do it

I wanted to say that it's necessary to define the collapsed face explicitly. (as I read it in the guide)

And one thing I wanted to say at first when I saw your dict (but I forgot it) :

I think you have to write:
Code:
        inlet
            {
            type patch; 
            faces 
            ( 
                (4 0 1 4) 
            ); 
        }
Instead of:
Code:
 
patch
inlet
(
 (4 0 1 4)
)
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Old   Yesterday, 17:36
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I did.

Take a look at this example:
https://openfoamwiki.net/index.php/M...s/AxiSymmetric

The normal direction of the outlet is in the "wrong direction". If you change that, the case won't work. Everything else you mentioned was in this case. The empty face. The way of defining faces for the new version of openFOAM

Quote:
Originally Posted by alexB View Post
there is no try... do it

I wanted to say that it's necessary to define the collapsed face explicitly. (as I read it in the guide)

And one thing I wanted to say at first when I saw your dict (but I forgot it) :

I think you have to write:
Code:
        inlet
            {
            type patch; 
            faces 
            ( 
                (4 0 1 4) 
            ); 
        }
Instead of:
Code:
 
patch
inlet
(
 (4 0 1 4)
)
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