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-   -   Arc-edge on wedge-block not possible? (http://www.cfd-online.com/Forums/openfoam-meshing-blockmesh/105496-arc-edge-wedge-block-not-possible.html)

A.A. August 1, 2012 06:56

Arc-edge on wedge-block not possible?
 
Hi,

I have created a mesh which has wedge blocks (blocks with only 6 vertices) but when I define an arc-edge on the wedge it is ignored and not shown in ParaFoam. the edge is shown as straight line.

Is it not possible to create arc-edges on wedge-blocks?

And if so, is there another possibility to get curved edges on a wedge-block?

Thanks in advance,
Alexander

anon_a August 1, 2012 08:00

It is definitely possible, I have done that.
Can you post your blockMesh?

A.A. August 2, 2012 04:39

I have j wedges and on the two edges which are opposite to the vertices that fall together I define an arc like : arc <vertex1> <vertex2> <interpolationpoint koordinates>.

I have this problem an all my wedges in my code.

@anon_a: Today I am working on another machine unfortantly I have no access to my blockMeshDict-file.

Mybe for wedges there is another command than arc ... ... ... to define arcs?

Regards,
Alex

anon_a August 2, 2012 06:21

1 Attachment(s)
An example blockMeshDict.m4 is attached.
Use
Code:

m4 blockMeshDict.m4 > constant/polyMesh/blockMeshDict
to create the real blockMeshDict.

I hope this is what you were looking for.


EDIT: something was wrong with uploading the file, I finally had to rename it to blockMeshDict.txt

aujamal20 January 20, 2013 14:54

Dear
I am trying to create edges in the following blockMeshDict file which creates a simple hex block (cavity tutorial). As stated in the user guide that the edges option arc produces the circular arc with single interpolation point but its not working in my case. Please let me know how to handle this.

Quote:

/*--------------------------------*- C++ -*----------------------------------*\
| ========= | |
| \\ / F ield | OpenFOAM: The Open Source CFD Toolbox |
| \\ / O peration | Version: 2.1.0 |
| \\ / A nd | Web: www.OpenFOAM.org |
| \\/ M anipulation | |
\*---------------------------------------------------------------------------*/
FoamFile
{
version 2.0;
format ascii;
class dictionary;
object blockMeshDict;
}
// * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * //

convertToMeters 1;

vertices
(
(0 0 0)
(1 0 0)
(1 1 0)
(0 1 0)

(0 0 0.1)
(1 0 0.1)
(1 1 0.1)
(0 1 0.1)
);

edges
(
arc 5 6 (1.1 0.5 0.1)
arc 1 2 (1.1 0.5 0)
);

blocks
(
hex (4 5 1 0 7 6 2 3) (1 1 1) simpleGrading (1 1 1)
);



boundary
(
movingWall
{
type wall;
faces
(
(3 7 6 2)
);
}
fixedWalls
{
type wall;
faces
(
(0 4 7 3)
(2 6 5 1)
(1 5 4 0)
);
}
frontAndBack
{
type empty;
faces
(
(0 3 2 1)
(4 5 6 7)
);
}
);

mergePatchPairs
(
);

// ************************************************** *********************** //
Regards
Jamal

A.A. January 21, 2013 04:27

Hi aujamal20,

Just increase simple greading to (2 2 2) and you will get the circular edges.

Best,
Alex

colinB January 21, 2013 04:38

In my opinion the grading shouldn't be a problem.

It would be interesting to know the error message to see what is wrong.
If the error message give something like:

Foam Fatal Error
Keyword: 'blocks' undefined I would try to place the keyword edges and
appendages below the keyword blocks.

However if he normally compiles the mesh without errors I would increase
the number of cells on each edge (replace the (1 1 1 ) before the word
simpleGrading with (10 10 10) or something like that), otherwise
the mesh cannot calculate the arc, for no interpolation points are given.

I hope I could contribute

regards
Colin

aujamal20 January 21, 2013 05:22

Dear

It compiles normally with out giving any error. But this time I put edges next to blocks and if I increase the number of cells from (1 1 1) to (2 2 2) it will draw straight lines from the interpolation point to opposite vertices while I expect to have a circular arc through that interpolation point.


Quote:

blocks
(
hex (0 1 2 3 4 5 6 7) (1 1 1) simpleGrading (1 1 1)
);

edges
(
arc 1 2 (1.5 0.5 0)
arc 5 6 (1.5 0.5 0.1)
);
Quote:

blocks
(
hex (0 1 2 3 4 5 6 7) (2 2 1) simpleGrading (1 1 1)
);

edges
(
arc 1 2 (1.5 0.5 0)
arc 5 6 (1.5 0.5 0.1)
);
Quote:

blocks
(
hex (0 1 2 3 4 5 6 7) (20 20 1) simpleGrading (1 1 1)
);

edges
(
arc 1 2 (1.5 0.5 0)
arc 5 6 (1.5 0.5 0.1)
);
Regards
jamal
http://www.cfd-online.com/Forums/C:%...sktop%5Ccavity
http://www.cfd-online.com/Forums/dat...AASUVORK5CYII=

colinB January 21, 2013 05:38

Hm in the above mentioned post there is no explicit question
and the information still is very limited.

You might want to provide a picture which illustrates your problem.

On the other hand I want you to redirect you to my previous post,
where I stated that the number of cells per edge is somehow related
to the display of certain edge types.

regards

aujamal20 January 21, 2013 05:44

3 Attachment(s)
Dear
I am trying to ask that in the first figure I have

Quote:

blocks
(
hex (0 1 2 3 4 5 6 7) (1 1 1) simpleGrading (1 1 1)
);

edges
(
arc 1 2 (1.5 0.5 0)
arc 5 6 (1.5 0.5 0.1)
);
and this does not produce any circular edge.

then I increase the number of cells in x1 & x2 direction and it create linear lines joining interpolation point to opposite vertices rather than an circular arc. I think it should produce an arc at this point or not???

Quote:

blocks
(
hex (0 1 2 3 4 5 6 7) (2 2 1) simpleGrading (1 1 1)
);

edges
(
arc 1 2 (1.5 0.5 0)
arc 5 6 (1.5 0.5 0.1)
);
and last figure correspond to the following file and still does not produce circular arc .

Quote:

blocks
(
hex (0 1 2 3 4 5 6 7) (20 20 1) simpleGrading (1 1 1)
);

edges
(
arc 1 2 (1.5 0.5 0)
arc 5 6 (1.5 0.5 0.1)
);
please let me know if i am making any blunder.

Thanks


http://www.cfd-online.com/Forums/dat...AAAElFTkSuQmCC

colinB January 21, 2013 09:12

I don't know what you are complaining about,
the last picture looks really nice!

The other pictures:
You only show the outline which is a simplified representation of the
geometry, which only shows the outer extends, but not the real geometry.
So the results are hardly comparable.
You should also print the surface of the to see what is really going on.
But even then I guess your geometry won't look like a circle, for
you are using to few cells.

However to complete the understanding of blockMesh:
Each cell has straight edges (somebody may correct me if I'm wrong),
so If you define an arc with one cell (1 1 1) then it still will be a square.
In order to get your block, arc shaped you have to use more cells,
which will align to the previous defined circle!

So this is why your pictures look more and more like a circle.

aujamal20 January 21, 2013 12:34

2 Attachment(s)
Dear colinB

Thanks for your patience and responses on my inquries. Actually what I was thinking was that by using an arc option in edges, a geometry with circular edges could be created even with one cell . And as u told that each cell has straight edges and to have circular edge i need to define more cells. Now i get the idea.
Onec again thanks alot......

Regards
Jamal

xiyuqiu March 5, 2013 21:45

If the angle is small, the line may look like a straight line. Yes, you can do it with arc. google OpenFoam pipe flow tutorial, there is a nice example of wedge (2D-axis symmetric) made by blockMesh.


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