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Strange boundaries for k and epsilon

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Old   December 16, 2008, 09:55
Default Hi, I have a pipe looking l
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Henning Wilhelmi
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Hi,

I have a pipe looking like this:



and its extruded along the flow direction (z-axis).

When I run simpleFoam (3000 Steps) I get unrealistic values for k(at least 184 though u = 3.725 m/s). Also near the boundaries they look strange. k should go back to 0 and epsilon should rise constantly.



I made a simpler case with a 2D channel and a similar mesh. Here the results look quite good.



Any idea what i am doing wrong?

B.c.s for k and epsilon are zeroGradient (similar to the tutorial cases in simpleFoam / turbFoam) and just for the internal field I gave values. I also tried values on inlet but then I get an error message saying I need zeroGradient at inlet patch.

Thanks for your help

Henning
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Old   December 16, 2008, 11:24
Default what turbulence model do you u
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Pierre Le Fur
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what turbulence model do you use?

Have you had a look at boundaryFoam and its tutorial? Even channelOodles. That might help.


Pierre
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Old   December 16, 2008, 15:10
Default Why don't you try a different
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Juan Fernando Duque Lombana.
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Why don't you try a different mesh configuration, check O-Grid configuration, that might help.
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Old   December 17, 2008, 06:07
Default I am using the classical k-eps
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Henning Wilhelmi
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I am using the classical k-epsilon model.

I took a look on boundaryFoam. It uses zeroGradient b.c. for both, k and epsilon as well. channelOodles didn't help me that much since it is LES and i am not so familar with LES.

And changing the mesh ... well, I don't like to use O-Grid for this solution since I would prefer a mesh that can be made finer at the boundaries easyly.

Maybe any other ideas?

Anyhow, thank you very very much for your help so far.

Henning
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Old   January 7, 2009, 03:54
Default Well, found my problem. Did pa
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Henning Wilhelmi
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Well, found my problem. Did patch instead of wall in blockMeshDict. It's always the simple things that make life so interesting ;)
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