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Old   January 9, 2004, 13:14
Default periodic fully developed flow in pipe
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I am trying to do a very basic simulation. It is to obtain fully developed flow in a pipe of constant cross section.I want to biuld the mesh so that there are periodic bcs. This way I don't need to biuld a very long pipe.

How do I build such a mesh?

I have tried linking the in and out and then meshing. However, the resulting mesh is only on the faces and the pipe wall, not in the volume even though I requested a volume mesh.

Can anyone help with this very simple dilema?

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Old   January 12, 2004, 05:12
Default Re: periodic fully developed flow in pipe
Andrew Garrard
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well, periodic, I assume that you are doing a 3D problem, if you request a volume mesh in gambit, then you should either get a volume mesh or an error tell you why a mesh has not been generated in the bottom part of the screen. What is the error you are recieving?
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Old   January 12, 2004, 07:58
Default Re: periodic fully developed flow in pipe
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Yes. 3D pipe. When I have not mesh on a face and request a volume mesh the error is: Face.1 could not be converted to a submappable region.

When I first mesh a face and then request a mesh of the volume I get the same error.

I'm not sure what I'm doing wrong. I just want to have a 3D pipe with periodic bcs so I can obtain fd flow profile.
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Old   January 12, 2004, 10:38
Default Re: periodic fully developed flow in pipe
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is there any hole in face 1. are number of nodes equal on opposite sides?
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Old   January 12, 2004, 12:53
Default Re: periodic fully developed flow in pipe
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There does not appear to be any hole in the face. The number of nodes are the same on both faces.

To create the geometry I simply chose to create a volume on a predefined primative, choosing cylinder.

Then I go to mesh and choose to mesh the first end face. Then go to mesh the volume choosing the volume and the meshed end face as the source.

I get the same error.

What am I doing wrong?
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Old   January 12, 2004, 16:57
Default Re: periodic fully developed flow in pipe
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My preferred way to mesh any cylindrical area to get a good mesh but may not work for this problem:
  • Use a face plan larger than your cylinder that cuts through it at the centerline.
  • Use the face-split to split the circular faces with this face (connected and retained, but not bidirectional).
  • Use the split line on each of the 2 new edges to split the line exactly 0.5 along it's length (that is, adding the center point to each face now).
  • Under the mesh face tool, set this new point for each of the 4 new faces to be a tri-element vertex.
  • Mesh the radii edges as desired. (Fixed interval is good, but in a pipe flow problem, you probably want to have a finer edge near the edge/wall - you could also use a boundary layer specification here if you need better control on the fineness of this mesh) - Make sure the number of edge points is even.
  • Mesh the circumfrence of the faces as desired, but make sure the number of mesh points is even.
  • Now mesh each of the 4 end faces. This should give you, by default, a nice radial pattern from the center point.
  • Mesh the lengthwise edge as desired
  • Mesh the volume at this point (the other face, along the body of the cylinder, will be generated automatically) using the hex/wedge/cooper scheme.
I've yet to have any problems when generating a system in this fashion, as opposed to letting Gabmit try to generate the end-cap face mesh which is typically quad/pave, and tends to be ugly. This gives you regular mesh elements near the walls all along the circumfrence of the tube.
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