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

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October 10, 2013, 02:02
the correct Type for axis of pipe in a 3D case
#1
Member

Arjang Behnoud
Join Date: Oct 2012
Posts: 61
Rep Power: 7
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;
minY            #calc "-1.0*\$y";
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
Attached Images
 after rescale Data.jpg (14.5 KB, 14 views) before resclae Data.jpg (13.1 KB, 10 views)

 October 11, 2013, 01:24 #2 Member   B T KANNAN Join Date: Jul 2011 Location: CHENNAI (MADRAS), INDIA Posts: 54 Rep Power: 8 Dear Arjang Behnoud,Try type "empty" for axis !! -- KANNAN

 October 12, 2013, 02:02 #3 Member   Arjang Behnoud Join Date: Oct 2012 Posts: 61 Rep Power: 7 first I've tried empty type for axis.but It was not good .

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