CFD Online Discussion Forums - [blockMesh] Cannot view arc edge in ParaView

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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.

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.

Quick answers:

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 );
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.

Quote:

Originally Posted by wyldckat (Post 573254)

Quick answers:

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 );
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

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.

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!;)