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Old   March 19, 2022, 04:00
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Matteo
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Hi guys,
I have a question about wall functions in Openfoam. If I create a mesh in Salome with viscous layer 2D that average yPlus is about 3 (y+ ~ 3), do I need wall function in my scripts (omega script). I found that if you set up very fine mesh than wall functions will automatically recognize it and not be activated in your simulation. Is that true? I hope I was enough clear...
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Old   March 19, 2022, 09:09
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Uwe Pilz
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Most probably, you don't need a wall function. Or more accurate: A wall function may introduce errors. The wall function increases the wall shearing stress, which is too low if a large y+ is used. If y+ is around unity, the simulation takes this into account automaticly. If you use it in such a case, you get a too high value of wall shear stress.
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Old   March 19, 2022, 11:14
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Ok thank you for explanation but I have one more question. If there is no need for wall functions, how I can disable them. For example: there is script "nut" and on default it says "type nutLowReFunction". What I have to set, " type fixedValue; value uniform 0"?
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Old   March 19, 2022, 11:26
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OF does not reduce velocity near walls, but increases viscosity. If you have y+ around unity you may set nut to zero. Otherwise, zeroGadient may be used too.
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