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Good 2D Airfoil Results?

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Old   January 28, 2011, 12:37
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  #21
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Felix L.
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Hello, José,


so changing the constant after a wall function definition actually alters the results? I've never tested this before, because in my eyes, this seems obsolete, since the wall functions actually are there to calculate a specific value at the wall so the user doesn't have to do this. Thanks for pointing that out, I'll have to investigate that further, when I find the time. Can you tell me how big the influence of changing this value is?

The equation for omega_wall you posted above is actually only applicable for the limiting case of y -> 0, i.e. lowRe meshes. I don't know which value of omega to specify when you're in the log layer (i.e. HighRe meshes) without using the wall function equations. This really puzzles me, because the prescribed constant value of omega really shouldn't matter at all. That's the whole point of wall functions.

Anyways, I'm a bit short on literature at the moment, but if you're able to, check the book of D.C. Wilcox. It's got a whole chapter dedicated to wall BCs for common 2-eq-turbulence models and I'm sure it'll help you out. I can't give you any more advices at the moment.

Regarding your other question: for steady state problems (assuming you have one), all boundary conditions affect the solution of the partial differential equations. The initial conditions (i.e. internal field values) should only influence the rate of convergence.


Greetings,
Felix.
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Old   May 8, 2011, 21:22
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Saxwax
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Hi Felix and José,

Has there been any follow up regarding the use of different values for omega when using a wall function boundary condition and how this can effect the results?

Cheers,
D.
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Old   May 9, 2011, 04:05
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José
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Hi!

The only wall function I have used in my computations using Low-Re meshes has been omegaWallFunction and changing the value defined in there does not affect the results. I have not tried OF with the other wall functions. I am sorry.

Regards,

José
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