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Old   October 28, 2009, 06:02
Default yPlus query
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varun
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Hi,

I have a basic query regarding the yPlus value and the associated(or appropriate) turbulence model, I wish to use the k-omega+SST model. What should be the appropriate yPlus value for good functioning of this model on openFoam. I have read in several threads that for K-epsilon model the yPlus should be in the log layer (y+>10). Is it the same case with komega+SST or should it be in the laminar sub-layer?

thnX!!
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Old   October 28, 2009, 08:06
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Simon Lapointe
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The kOmegaSST model in OpenFOAM uses wall functions and thus requires a high y+ value. However, in 1.5-dev there is a kOmegaSST_LowRe which, I think, can resolve the near-wall region and should be used with a small y+.

Hope this helps
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Old   October 28, 2009, 10:20
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Hi Simon,

I will try this out.

ThanX!!

Last edited by vw.cfd; October 28, 2009 at 10:41.
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Old   October 29, 2009, 08:53
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Hi Simon,

I tried your suggestion on openfoam 1.5-dev,

I obtain this error message:

Unknown RASModel type kOmegaSST_LowRe
Valid RASModel types are :
15
(
NonlinearKEShih
kEpsilon
realizableKE
LienCubicKELowRe
LienLeschzinerLowRe
LaunderSharmaKE
laminar
SpalartAllmaras
LienCubicKE
LamBremhorstKE
RNGkEpsilon
LRR
QZeta
LaunderGibsonRSTM
kOmegaSST
)

Which turbulence model did you mean exactly?

ThnX!!
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Old   October 29, 2009, 10:24
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Simon Lapointe
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Hi varun,

The kOmegaSST_LowRe model has been added recently to OpenFOAM-1.5-dev so you need to update your OpenFOAM (or download the model source code) to get it.
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Old   February 18, 2010, 10:08
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Claus Meister
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Hey, foamers!

I am already using OpenFOAM 1.6. The mentioned mole does not exist.

Cheers
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Old   February 22, 2010, 06:44
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bump - any new info on this?
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Online free airfoil-mesher for OpenFOAM here
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Old   February 23, 2010, 04:25
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Tammo Wenterodt
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The source of the kOmegaSST_lowRe model can be downloaded here:
http://openfoam-extend.svn.sourcefor.../?pathrev=1415
it does not directly compile with 1.6, though only little changes neccessary:

at kOmegaSST_LowRe/kOmegaSST_LowRe.C line 171 add
Code:
kappa_
     (
         dimensioned<scalar>::lookupOrAddToDict
       (
           "kappa",
            coeffDict_,
           0.41
       )
     ),
and at line 313 add
Code:
kappa_.readIfPresent(coeffDict_);
in kOmegaSST_LowRe/kOmegaSST_LowRe.H add at line 131
Code:
dimensionedScalar kappa_;
I have used it in 1.6 a lot so far in 1d and 2d problems obtaining very good results (pipes, channels, plate heat exchangers, tube bundle heat exchangers).
BUT I face major problems in 3d geometries, where the model results in distinct pressure fronts in the domain, which then make the calculation crash.

I'd be glad for any ideas on that!

//Tammo

Last edited by wenterodt; February 23, 2010 at 04:52.
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Old   February 23, 2010, 07:15
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Claus Meister
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Hello wenterodt,

could you please post the procedure to install it in OpenFOAM-1.6?

Cheers,

Claus
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Old   February 23, 2010, 08:19
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Tammo Wenterodt
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Basically just write Make/files and Make/options, compile (wmake libso) and add a line to the controlDict

The procedure is pretty much the same as described here:
http://www.tfd.chalmers.se/~hani/kurser/OS_CFD_2008/implementTurbulenceModel.pdf

// Tammo
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Old   March 3, 2010, 16:12
Default Wall function on LowRe model
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Hello Tammo,


have you any experience in nut boundary conditions on kOmegaSST_LowRe RAS model. It is zeroGradient or some nut wall function?


Thanks.
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Old   March 10, 2010, 15:39
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Claus Meister
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Hey Foamers!

I do not understand the purpose of yPlus. I found that tool yPlusRAS and executed. I got this values, but what should I do with these? I have been watching in many books.

Cheers,

Claus
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