CFD Online Discussion Forums - [blockMesh] round tube

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- - [blockMesh] round tube - checkMesh error (https://www.cfd-online.com/Forums/openfoam-meshing/125979-round-tube-checkmesh-error.html)

round tube - checkMesh error

When i made a straight tube and "checkMesh" i receive no errors. But when i add a 90° round tube on top, "checkMesh" returns 4 errors (please see below). I made a round tube using this instructions: http://www.cfd-online.com/Forums/ope...blockmesh.html

When i run paraFoam, everything looks nice. I tried to change the tube grading but this didn't solve the "High aspect ratio" problem. I have no idea how could i solved the non-orthogonality error - isn't this obveous that the faces will be non orthogonal if the tube is not straight?

Any idea how can i solve this problem?

Regards
Klemen

--------------------------
Checking geometry...
Overall domain bounding box (-0.008 -0.00654102 0.002) (0.00654102 0.00654102 0.0339986)
Mesh (non-empty, non-wedge) directions (1 1 1)
Mesh (non-empty) directions (1 1 1)
Boundary openness (-1.31732e-17 1.60882e-17 2.02306e-16) OK.
***High aspect ratio cells found, Max aspect ratio: 7.93329e+192, number of cells 330
<<Writing 330 cells with high aspect ratio to set highAspectRatioCells
Minimum face area = 1.05207e-23. Maximum face area = 6.85601e-07. Face area magnitudes OK.
Min volume = 1.66667e-300. Max volume = 1.87778e-10. Total volume = 2.065e-06. Cell volumes OK.
Mesh non-orthogonality Max: 180 average: 17.3038
*Number of severely non-orthogonal faces: 478.
***Number of non-orthogonality errors: 1103.
<<Writing 1581 non-orthogonal faces to set nonOrthoFaces
***Error in face pyramids: 2244 faces are incorrectly oriented.
<<Writing 1189 faces with incorrect orientation to set wrongOrientedFaces
***Max skewness = 8.04445, 7 highly skew faces detected which may impair the quality of the results
<<Writing 7 skew faces to set skewFaces
Coupled point location match (average 0) OK.
Failed 4 mesh checks.

Quote:

Originally Posted by fogl (Post 460672)

Reduce non-orthogonality, skewness etc.,
Try increasing the number of cells in the round tube.
--
KANNAN

hello klemen.
i have the same problem. can you solve this problem??
Thanks.

Regards

Hello Ali,

I think i solved the problem by defining the circle (tube cross section) from five patches - a square in the middle and four curved trapezoids around the square.

I don't have the access to my computer at the moment, but i can check it next week - let me know if you don't succeed.

Regards
Klemen

Thank you very much Klemen.

My blockMesh file is:
code:

Code:

/*--------------------------------*- C++ -*----------------------------------*\

| =========                 |                                                 |

| \\      /  F ield         | OpenFOAM: The Open Source CFD Toolbox           |

|  \\    /   O peration     | Version:  2.2.1                                 |

|   \\  /    A nd           | Web:      www.OpenFOAM.com                      |

|    \\/     M anipulation  |                                                 |

\*---------------------------------------------------------------------------*/

FoamFile

{

    version     2.0;

    format      ascii;

    class       dictionary;

    object      blockMeshDict;

}

// * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * //



convertToMeters 0.01;



vertices        

(

    (0 8 2)        

    (10 0 1.5)    

    (10 3 2)    

    (1 8 2)    

    (0 8 0)    

    (10 0 0.5)    

    (10 3 1)    

    (1 8 0)    

);

blocks          

(

    hex (0 1 2 3 4 5 6 7) (40 15 10) simpleGrading (1 1 1)

);



edges           

(

);



boundary

(

    inlet

    {

        type patch;

        faces

        (

            (0 4 7 3)

        );

    }

    outlet

    {

        type patch;

        faces

        (

            (1 2 6 5)

        );

    }

    Wall

    {

        type wall;

        faces

        (

            (0 1 2 3)

            (4 5 6 7)

            (3 2 6 7)

            (0 1 5 4)

        );

    }

);



mergePatchPairs

(

);



// ************************************************************************* //

When i run blockMesh with this vertices, i get the error massage:

Code:

Checking geometry...

    Overall domain bounding box (0 0 0) (0.1 0.08 0.02)

    Mesh (non-empty, non-wedge) directions (1 1 1)

    Mesh (non-empty) directions (1 1 1)

    Boundary openness (5.08774e-17 -1.73343e-16 -2.05592e-16) OK.

 ***High aspect ratio cells found, Max aspect ratio: 2.76503e+194, number of cells 6000

  <<Writing 6000 cells with high aspect ratio to set highAspectRatioCells

    Minimum face area = 8.95863e-07. Maximum face area = 6.3631e-06.  Face area magnitudes OK.

    Min volume = 2e-300. Max volume = 2e-300.  Total volume = 1.2e-296.  Cell volumes OK.

    Mesh non-orthogonality Max: 180 average: 157.305

 ***Number of non-orthogonality errors: 16850.

  <<Writing 16850 non-orthogonal faces to set nonOrthoFaces

 ***Error in face pyramids: 36000 faces are incorrectly oriented.

  <<Writing 19150 faces with incorrect orientation to set wrongOrientedFaces

    Max skewness = 3.57447 OK.

    Coupled point location match (average 0) OK.



Failed 3 mesh checks.



End

But when i change the vertices(while the geometry remain approximately constant), like this :
vertices
(
(-5 4 0) //0
(0 -1 0) //1
(0 0.5 0.5) //2
(-4 4 0) //3
(-5 4 2) //4
(0 -1 0.5) //5
(0 0.5 1) //6
(-4 4 2) //7
);

everything is ok. I'm confused. I don't know how i solve this problem. Do you know how solve this problem?
Thank you very much for your help.

Best regards,
Ali