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the correct Type for axis of pipe in a 3D case

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Old   October 10, 2013, 02:02
Default the correct Type for axis of pipe in a 3D case
  #1
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Arjang Behnoud
Join Date: Oct 2012
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Hi Everyone

for simulating laminar duct flow in a pipe I've model only a quarter of pipe and the blockMeshDict is like below:
Code:
convertToMeters 1;
//- half angle of wedge in degrees
halfAngle 45.0;
//- Radius of pipe [m]
radius 0.00625;
radHalfAngle    #calc "degToRad($halfAngle)";
y               #calc "$radius*sin($radHalfAngle)";
minY            #calc "-1.0*$y";
z               #calc "$radius*cos($radHalfAngle)";
minZ            #calc "-1.0*$z";
//-length of pipe [m]
l 1;
vertices
(
    (0.0    0.0 0)      //0
    ($l     0.0 0)
    ($l     0.0 0)      //2
    (0.0    0.0 0)
    (0.0    $minY $z)   //4
    ($l     $minY $z)
    ($l     $y $z)      //6
    (0.0    $y $z)
);

blocks
(
    // inlet block
    hex (0 1 2 3  4 5 6 7) (300 20 20) simpleGrading (1 1 .2)
);

edges
(
    arc 4 7 (0 0 $radius)
    arc 5 6 ($l 0 $radius)
);

boundary
(
    inlet
    {
        type patch;
        faces
        (
            (0 4 7 3)
        );
    }

    outlet
    {
        type patch;
        faces
        (
            (1 2 6 5)
        );
    }

    side1
    {
        type cyclic;
        neighbourPatch side2;
        faces
        (
            (0 1 5 4)
        );

        transform rotational;
        rotationAxis (1 0 0);
        rotationCentre (0 0 0);
    }

    side2
    {
        type cyclic;
        neighbourPatch side1;
        faces
        (
            (7 6 2 3)
        );

        transform rotational;
        rotationAxis (1 0 0);
        rotationCentre (0 0 0);
    }

    walls
    {
        type wall;
        faces
        (
            (4 5 6 7)
           //(3 2 1 0)
        );
    }

   axis
    {
        type slip;
        faces
        (
             (3 2 1 0)
        );
    } 
);
once I omit the axis because the case is 3D but when I type blockMesh in terminal, I find out that one defaultFace is created and its type is empty finally I decide Slip type for axis but now after running the solver when I open parafoam it is obvious that the flow is not fully developed at outlet of pipe(it should be fully developed).

(pictures are attached)

now I want to know what is the problem, slip type is not correct for axis or maybe the quality of mesh (300 20 20) is not good?

Thanks.
Arjang
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Old   October 11, 2013, 01:24
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  #2
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B T KANNAN
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Location: CHENNAI (MADRAS), INDIA
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Dear Arjang Behnoud,Try type "empty" for axis !!

--
KANNAN
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Old   October 12, 2013, 02:02
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Arjang Behnoud
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first I've tried empty type for axis.but It was not good .
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