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Understanding LESDeltas

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Old   December 6, 2011, 11:28
Default Understanding LESDeltas
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Francesco Capuano
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Hi everyone,
I am trying to understand deeply the implementation of LES into OpenFoam, and I have a problem with the vanDriestDelta and the PrandtlDelta codes: I cannot understant the Cdelta_ coefficient in the following formulas for calculating delta:

(kappa_/Cdelta_)*wallDist(mesh_).y()
(kappa_/Cdelta_)*((scalar(1) + SMALL) - exp(-y/ystar/Aplus_))*y

Except for Cdelta_, these are the well-known Prandtl's mixing length and van Driest's damping function formulas, respectively. The default value for Cdelta_ is set to be 0.158: do any of you know where this value come from?

Thanks in advance,
Francesco
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Old   February 1, 2014, 01:06
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caoyong
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Dear Francesco,
These days, I am also confused about the Cdelta_ when I want to use the vanDriest damping function for LES. Have you found any information about it?
Another problem is, usually we use the vanDriest function to multiply the cube root of volume for LES near the wall. But herein, Openfoam use the damping function multiply the mixing length (kappa*y), which is often utilized in RANS models.
Could you give some any hint?
Thanks very much.
Yong
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Old   July 26, 2014, 13:11
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Hi,

== 1 ==
Please look at p. 260 of his PhD thesis:
http://powerlab.fsb.hr/ped/kturbo/Op...ersPhD2006.pdf
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