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February 4, 2010, 15:00 
LES kOmegaSSTSAS / looking for RASProperties

#1 
Senior Member
PierreOlivier Dallaire
Join Date: Mar 2009
Location: Montreal, Quebec, Canada
Posts: 187
Rep Power: 10 
Hi,
I'm trying to run a sim using LES kOmegaSSTSAS but facing this strange error / anybody experienced that before ? Thanks Create time Create mesh for time = 0 Reading field p Reading field U Reading/calculating face flux field phi Selecting incompressible transport model Newtonian Selecting turbulence model type LESModel Selecting LES turbulence model kOmegaSSTSAS kOmegaSSTSASCoeffs { alphaK1 0.85034; alphaK2 1; alphaOmega1 0.5; alphaOmega2 0.85616; gamma1 0.5532; gamma2 0.4403; beta1 0.075; beta2 0.0828; betaStar 0.09; a1 0.31; c1 10; Cs 0.262; alphaPhi 0.666667; zetaTilda2 1.755; FSAS 1.25; Cmu 0.09; } Courant Number mean: 0.003328494907 max: 0.04563852373 Starting time loop Time = 0.1 Courant Number mean: 0.003328494907 max: 0.04563852373 deltaT = 0.1 smoothSolver: Solving for Ux, Initial residual = 1, Final residual = 0.0001447730244, No Iterations 1 smoothSolver: Solving for Uy, Initial residual = 1, Final residual = 0.004463225608, No Iterations 1 smoothSolver: Solving for Uz, Initial residual = 1, Final residual = 0.003346085113, No Iterations 1 GAMG: Solving for p, Initial residual = 1, Final residual = 0.04815958026, No Iterations 4 GAMG: Solving for p, Initial residual = 0.05136590869, Final residual = 0.001241589961, No Iterations 1 time step continuity errors : sum local = 7.87914026e05, global = 9.572829191e06, cumulative = 9.572829191e06 GAMG: Solving for p, Initial residual = 0.007659904341, Final residual = 0.0001102955053, No Iterations 2 GAMG: Solving for p, Initial residual = 0.006646878643, Final residual = 3.869521047e07, No Iterations 6 time step continuity errors : sum local = 2.623671733e08, global = 3.116971313e09, cumulative = 9.575946162e06 smoothSolver: Solving for k, Initial residual = 0.9999999999, Final residual = 0.0009974693262, No Iterations 1 > FOAM FATAL ERROR: request for RASModel RASProperties from objectRegistry region0 failed available objects of type RASModel are 0 ( ) 

February 4, 2010, 16:15 
SAS model

#2 
New Member
Kyungrock Kim
Join Date: Jun 2009
Posts: 20
Rep Power: 9 
Dear Dallaire
It's pretty weird. OF is asking RASModel type. It might be worked in different machine. Anyway, it's a strange bug. Best wishes Kyungrock 

May 19, 2010, 12:36 

#3 
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Jiang Lijun
Join Date: Mar 2009
Posts: 14
Rep Power: 10 
Hi, Dallaire
Did you solve this problem? I encounter the same problem. ^_^ Lijun 

May 19, 2010, 13:03 

#4 
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Jiang Lijun
Join Date: Mar 2009
Posts: 14
Rep Power: 10 
Hi, Dallaire
I think I found what's the problem. Maybe you used the wrong wall treatment in omega as me, did you ues "omegaWallFunction"? This BC isn't defined in LES models, I think. Best wishes, Lijun 

June 16, 2010, 15:52 

#5 
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Alex
Join Date: Apr 2010
Posts: 32
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Yes, this is because you have used wall functions in 0/k and/or 0/omega


August 17, 2011, 13:56 

#6 
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Phil
Join Date: Mar 2011
Location: West Des Moines, Iowa, U.S.A.
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So which patchField type (wall treatment) are we supposed to use for omega?
It isn't obvious to me which patchField types to use. I checked the tutorials (OF2.0.0 and OF1.7.1) and couldn't find anything involving kOmegaSSTSAS. I'm using "kqRWallFunction" for the "k" patchField type, and the solver (OF2.0.0 pimpleFoam and pisoFoam) successfully runs through the kequation, but "bombs" on the omegaequation (as noted above by PierreOlivier Dallaire) Thanks. Phil 

January 4, 2012, 15:44 

#7 
Senior Member

Hi Phil,
Did you ever resolve this problem? I am looking at it now because one of the students in our group is using this model and came to me with a question on this. I would recommend two possible solutions, 1. use fixedValue for k and omega and make sure that the mesh is sublayer resolved so that you can use classical values near wall values. 2. hack the code and adapt the RAS b.c. for omegaWallFunction to your kOmegaSSTSAS model. Eric 

February 29, 2012, 06:41 

#8 
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Join Date: Mar 2009
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Hi everybody,
Did anyone tried, as Eric suggested, to adapt the omegaWallFunction to the kOmegaSSTSAS turbulence model ? As for now, I use a viscousresolved grid and a fixedValue for omega, but it is quite tricky in some cases. Cheers, Fabien 

March 23, 2012, 03:36 
omegaWallFunction for kOmegaSSTSAS

#9 
Member
Masashi Ohbuchi
Join Date: Oct 2009
Posts: 74
Rep Power: 9 
Hi,
I've tried to implement LESversion omegaWallFunction for kOmegaSSTSAS model as follows. 1. copy RAS/derivedFvPatchFields/wallFunctions/omegaWallFunctions/omegaWallFunction to LES/derivedFvPatchFields/wallFunction 2. replace "RASModel" to "LESModel" in source code of omegaWallFunction 3. modify LESModel.H #include nearWallDist.H protected: nearWallDist y_; public: // Member functions // Return the near wall distances const nearWallDist& y() const { return y_; } 4. modify kOmegaSSTSAS.C void kOmegaSSTSAS::correct(const tmp<volTensorField>& gradU) { volScalarField G("LESModel::G", nuSgs_*0.5*S2); Am I correct? 

March 23, 2012, 11:40 

#10 
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Timo K.
Join Date: Feb 2010
Location: University of Stuttgart
Posts: 66
Rep Power: 9 
Hallo Masashi,
I think your coding of the omegaWallFunction should be correct. But how do you set your BC for omega in kOmegaSSTSAS.C (in fact, you don't)? In the RASversion this is done by: omega_.boundaryField().updateCoeffs(); after G and you set it to the matrix after the omega equation: omegaEqn().boundaryManipulate(omega_.boundaryField ()); I am not sure if you can transfer the procedure from RASSST to SAS, because the arrangement of the omega and kequation is not the same! Has anybody an opinion about that? Best, Timo 

March 23, 2012, 12:13 

#11 
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Timo K.
Join Date: Feb 2010
Location: University of Stuttgart
Posts: 66
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BTW: I think the G is also wrong in version 2.0 (correct me if I am wrong)
if volScalarField S2(2.0*magSqr(symm(gradU()))); G should be like this: volScalarField G = nuSgs_*S2; and not divided by 2 G should be the same as in RAS! Any opinions? Best PS: @Masashi and all SASusers: have you validated the SAS model against a test case? 

March 23, 2012, 21:21 
kOmegaSSTSAS

#12  
Member
Masashi Ohbuchi
Join Date: Oct 2009
Posts: 74
Rep Power: 9 
Hi, Timo
Thank you for your reply. I agree with you about the notation of G. But I've modified these code without much thought. And I've checked my implementation with attached example. Best regards, Masashi Obuchi. Quote:


April 12, 2012, 03:48 
Strange behavior of k and omega

#13 
Member
Timo K.
Join Date: Feb 2010
Location: University of Stuttgart
Posts: 66
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It's me again,
I've tested the kOmegaSSTSAS model on the channel flow Re_tau=395, initialized with a LES simulation. I encountered a strange behavior of the turbulent fields k and omega, after ~10 iterations those fields do NOT change any more, they stay completely unchanged. Also nuSgs does not change a lot any more (as it should corresponding to the turbulent structure). Any opinion on that? Best, Timo 

June 20, 2012, 09:33 

#14 
Senior Member

Hello everyone,
thanks for all your inputs concerning the kOmegaSSTSAS model. If I understand correctly, the model is still not usable for grids with near wall resolutions of y+>30, at least not without implementing a modified wall function.. Is that right? Louis 

June 21, 2012, 04:01 

#15 
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Tibor Nyers
Join Date: Jul 2010
Location: Hungary
Posts: 91
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Hi Louis,
I have reported the problem and I got a very detailed explanation about the issue. bug report  kOmegaSSTSAS requests RASModel RASProperties 

June 21, 2012, 07:57 

#16 
Senior Member

Hi Tibor,
Thank you. I had read your bug report, and it indeed pretty much confirms that there is no High Reynolds models available for KomegaSSTSAS as of now, right? Louis Last edited by louisgag; June 21, 2012 at 09:18. 

June 21, 2012, 08:19 

#17 
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Tibor Nyers
Join Date: Jul 2010
Location: Hungary
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Yeah, that's my final conclusion as well.


July 20, 2012, 06:01 

#18 
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Jane L
Join Date: May 2012
Posts: 21
Rep Power: 6 
In that bug report mentioned above, it is stated, that this issue should be fixed in version 2.1.1. I'm still not able to use omegaWallFunction in LES. Did anyone of you check?
I'm still wondering why OpenFOAM doesn't complain about kqRWallFunction which isn't part of LES either. Any ideas? best regards! 

July 20, 2012, 10:31 

#19 
Senior Member

I don't think near wall treatment for the kOmegaSSTSAS is yet available.


March 21, 2014, 17:41 

#20 
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Philipp
Join Date: Jun 2011
Location: Germany
Posts: 1,297
Rep Power: 19 
Hi all, I hope some of you are still active in this forum.
The issue is still the same as I understand it. The SAS model indeed accepts the omega wall function nowadays (I think since 2.2) but doesn't evaluate it at all. This is really confusing. But: The two models differ just by this one Fsas term, right? So wouldn't it be sufficient, if we just make a copy of the RAS model directory and add this one term? All wall function usage would be correct then, I guess.
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