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periodicbc January 9, 2004 13:14

periodic fully developed flow in pipe
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?


Andrew Garrard January 12, 2004 05:12

Re: periodic fully developed flow in pipe
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?

periodicbc January 12, 2004 07:58

Re: periodic fully developed flow in pipe
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.

s January 12, 2004 10:38

Re: periodic fully developed flow in pipe
is there any hole in face 1. are number of nodes equal on opposite sides?

periodicbc January 12, 2004 12:53

Re: periodic fully developed flow in pipe
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?

MN January 12, 2004 16:57

Re: periodic fully developed flow in pipe
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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