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-   -   Cannot view arc edge in ParaView (http://www.cfd-online.com/Forums/openfoam-meshing-blockmesh/72213-cannot-view-arc-edge-paraview.html)

erlendg January 28, 2010 15:47

Cannot view arc edge in ParaView
 
I have tried several blockMesDict files trying to make a cylinder using arc. blockMesh seems to go fine, but the arc is not visible in paraview (version 3.6.1). Anyone experienced this ? I used an example from the user manual so I recon the use of arc should be ok.

iper88 November 13, 2015 13:09

I had the same problem with paraview 4.1.0

It is at the moment just a 1 cell try.
BlockMesh code runs but it doesn't show any arc.

Code:

L 288;
D 88;
R 100;
B 722;
C 222;
alpha 35.0;
CapL 50;
Dd 50;
nzp -50;
zp 50;

//declaración de distancias

Fd #calc "10*$L";
Bd #calc "20*$L";
Ud #calc "8*$L";

Ax #calc "$Fd-$CapL";
Bx #calc "$Fd+$R-($R+$CapL)*cos(45.0)";
Cx #calc "$Fd+$R-$R*cos(45.0)";

//Dx #calc "$Fd+$R";
//Ex #calc "$Fd+$R+$B";

Cy #calc "$Dd+$R+$D";
Dy #calc "$Dd+$R+$D+($R+$CapL)*sin(45.0)";

//Gy #calc "$Dd+$L";

Hy #calc "$Dd+$D+$R+$R*sin(45.0)";

//Ly #calc "$Dd+$L+$CapL";


convertToMeters 0.001;

vertices
(
    ($Ax $Cy $nzp)
    ($Fd $Cy $nzp)
    ($Cx $Hy $nzp)
    ($Bx $Dy $nzp)
    ($Ax $Cy $zp)
    ($Fd $Cy $zp)
    ($Cx $Hy $zp)
    ($Bx $Dy $zp)
);

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

);

edges
(  arc 1 2 (#calc "$Fd+($R-$R*cos(20.0))" #calc "$Cy+$R*sin(20.0)" $nzp)
   
);

boundary
(

);

mergePatchPairs
(
);

I don't understand why this occurs.
Moreover, after perform checkMesh got 1 failure:
Code:

  ***Number of edges not aligned with or perpendicular to non-empty directions: 6
  <<Writing 8 points on non-aligned edges to set nonAlignedEdges

Can anyone help? thanks in advance.

wyldckat November 13, 2015 15:50

Quick answers:
  1. Arcs, splines and other complex edges are only meshed when there are enough discretization points. In other words, with only 2 points, the arc cannot exist:
    Code:

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

    );

  2. The error message refers to the fact that no patch was defined here:
    Code:

    boundary
    (

    );

    Therefore there is only one default patch, defined by default as of type "empty". Therefore, all 3 major directions are all empty and therefore there are no dimensions over which to solve the domain ;)
My advice: start with a working mesh from a tutorial and gradually make changes and test what each change does to the mesh.

iper88 November 14, 2015 11:37

Quote:

Originally Posted by wyldckat (Post 573254)
Quick answers:
  1. Arcs, splines and other complex edges are only meshed when there are enough discretization points. In other words, with only 2 points, the arc cannot exist:
    Code:

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

    );

  2. The error message refers to the fact that no patch was defined here:
    Code:

    boundary
    (

    );

    Therefore there is only one default patch, defined by default as of type "empty". Therefore, all 3 major directions are all empty and therefore there are no dimensions over which to solve the domain ;)
My advice: start with a working mesh from a tutorial and gradually make changes and test what each change does to the mesh.

Thanks for your quick answer Bruno.

Your explanation has been very useful because I realized that just changing the number of cells per each direction (x' y'), arcs are drawn.
so I changed like this:

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

Thanks a lot.
Best regards
Ivan

wyldckat November 14, 2015 11:44

Quick answer:
Quote:

Originally Posted by iper88 (Post 573303)
hex (0 1 2 3 4 5 6 7) (1 1 1) simpleGrading (20 20 1) //0

That affects only the way the cells are distributed along their directions.
I hope you wanted to write this:
Code:

hex (0 1 2 3 4 5 6 7) (20 20 1) simpleGrading (1 1 1) //0
Because this defines that 20 cells are to be used along the first 2 main directions of the block, and only 1 cell along the 3rd direction.

iper88 November 14, 2015 12:22

Quote:

Originally Posted by wyldckat (Post 573304)
Quick answer:

That affects only the way the cells are distributed along their directions.
I hope you wanted to write this:
Code:

hex (0 1 2 3 4 5 6 7) (20 20 1) simpleGrading (1 1 1) //0
Because this defines that 20 cells are to be used along the first 2 main directions of the block, and only 1 cell along the 3rd direction.

Of course, just a mistake while writing the post. I've already corrected. Thanks!;)


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