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Old   October 21, 2011, 14:34
Default Wall functions
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Deepchand Singh Negi
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What should be wall functions (in realizable K-Epsilon model) for
y+ < 1
y+= 5-10
y+> 30

And what exactly the physics behind the choosing these different wall functions
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Old   October 22, 2011, 00:13
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Hey,
You need not define any wall function in different flow regimes. In Enhanced wall function option Fluent will actually solve N-S eqns to find flow pattern (more accurate). Standard wall function is just an interpolation (less accurate).

But since Enhanced wall function actually solves the flow you have to make sure that your first grid point lies in distance y+ < 5 (viscous sublayer)

There is no y+ < 1 rule as u said.


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Old   October 22, 2011, 01:07
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thank it was useful

one more thing for enhanced wall function we need the first cell size with y+<5

say if i want or say created another geometry with y+=10 for first cell

and again another with y+=30 for first cell

what wall function should I use for those two cases (say Standard Wall Function or Non-Equilibrium wall function)
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Old   October 22, 2011, 01:28
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I don't know what is 'non-equilibrium wall fn', standard wall function is good enough for both the cases.
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Old   October 22, 2011, 01:41
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ok thanks buddy
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