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-   -   Axissymmetric pipe Simulation with unequal zero wall velocity (http://www.cfd-online.com/Forums/openfoam/66394-axissymmetric-pipe-simulation-unequal-zero-wall-velocity.html)

 Thomas Baumann July 14, 2009 05:41

Axissymmetric pipe Simulation with unequal zero wall velocity

3 Attachment(s)
Hallo all,

I built an axissymmetric mesh with the blockmesh utility. It is a pipe with an inlet and outlet, on top a wall, down is the axis and left and right are wedges.

Running with icofoam works, but looking at the velocity at the wall there are nonzero values.

I plotted the velocity-values in paraview.
I also used the sampledict with different interpolation schemes (cell, cellPoint, cellPointFace).
Plotting the wall surface shows again zero values.

Has anybody an idea?

Thanks, Thomas

 sega July 14, 2009 06:02

Quote:
 Originally Posted by Thomas Baumann (Post 222592) I plotted the velocity-values in paraview.
Looks like ParaView didn't plot the value directly at the wall.
Can you show us the result with with sample?

 Thomas Baumann July 14, 2009 07:28

3 Attachment(s)
Hallo,

here are the velocity-profils made by the sampledict with the three interpolation schemes: cell, cellPoint and cellPointFace.

The set was made by a uniform line with 40 values from r =0.9R until r = R.

 sega July 14, 2009 07:51

Instead of using a line with 40 points you can try using a midPointAndFace type, so you will get values at points corresponding to your discretization.
In this case you can even omit the nPoints-entry!

Something like this:

Code:

```interpolationScheme cellPointFace; setFormat    raw; surfaceFormat    foamFile; sets      (     line_horizontal     {         type            midPointAndFace;         axis            z;         start          (0.8838 0.8838 0);         end            (0.8838 0.8838 5);     } );```

 Thomas Baumann July 14, 2009 08:08

I have used midPointAndFace, too, but nothing changed. There is still nonzero velocity at the wall.

 sega July 14, 2009 10:41

I have played with the case but could not find a solution to this problem, at first glance.

Anyone got further ideas?

 Thomas Baumann July 15, 2009 04:36

I think the interpolation sheme is the problem. I changed in the sampledict the interpolationScheme to cell (constant over cells) and the type to midPoint (one Point per cell) and the results are much better. Plotting the velocity graphs with gnuplot show good results.

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