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Axissymmetric pipe Simulation with unequal zero wall velocity

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Old   July 14, 2009, 05:41
Default Axissymmetric pipe Simulation with unequal zero wall velocity
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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.
The radius is about one meter.

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
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Old   July 14, 2009, 06:02
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Quote:
Originally Posted by Thomas Baumann View Post
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?
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Old   July 14, 2009, 07:28
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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.
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File Type: txt pos_cellPointFace_U.txt (2.6 KB, 5 views)
File Type: txt pos_cellPoint_U.txt (2.6 KB, 1 views)
File Type: txt pos_cell_U.txt (2.6 KB, 2 views)
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Old   July 14, 2009, 07:51
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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);
    }
);
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Old   July 14, 2009, 08:08
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I have used midPointAndFace, too, but nothing changed. There is still nonzero velocity at the wall.
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Old   July 14, 2009, 10:41
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I have played with the case but could not find a solution to this problem, at first glance.

Anyone got further ideas?
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Old   July 15, 2009, 04:36
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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.

Last edited by Thomas Baumann; July 15, 2009 at 11:06.
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