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August 30, 2007, 06:04 |
Hi,
I'm not really sure it i
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#1 |
Member
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Hi,
I'm not really sure it is a bug (I'm still working with version 1.3 and so I didn't try it) but it seems to me that the new (1.4.1 release) compressible kOmegaSSTomega has wrong production terms for both omega and k equations (also dimensionally): /* this is the relevant part of the code volScalarField GbyMu = 2*mut_*(tgradU() && dev(symm(tgradU()))); volScalarField G = mut_*GbyMu; tmp<fvscalarmatrix> omegaEqn ( fvm::ddt(rho_, omega_) + fvm::div(phi_, omega_) - fvm::laplacian(DomegaEff(F1), omega_) == rhoGammaF1*GbyMu - fvm::SuSp((2.0/3.0)*rhoGammaF1*divU, omega_) - fvm::Sp(rho_*beta(F1)*omega_, omega_) - fvm::SuSp ( rho_*(F1 - scalar(1))*CDkOmega/omega_, omega_ ) tmp<fvscalarmatrix> kEqn ( fvm::ddt(rho_, k_) + fvm::div(phi_, k_) - fvm::laplacian(DkEff(F1), k_) == min(G, c1*betaStar*k_*omega_) - fvm::SuSp(2.0/3.0*rho_*divU, k_) - fvm::Sp(rho_*betaStar*omega_, k_) ); I guess that it should instead be something like: volScalarField G_DividedbyMu = 2*(tgradU() && dev(symm(tgradU()))); volScalarField G = mut_*G_DividedbyMu; tmp<fvscalarmatrix> omegaEqn ( fvm::ddt(rho_, omega_) + fvm::div(phi_, omega_) - fvm::laplacian(DomegaEff(F1), omega_) == rhoGammaF1*G_DividedbyMu - fvm::SuSp((2.0/3.0)*rhoGammaF1*divU, omega_) - fvm::Sp(rho_*beta(F1)*omega_, omega_) - fvm::SuSp ( rho_*(F1 - scalar(1))*CDkOmega/omega_, omega_ ) tmp<fvscalarmatrix> kEqn ( fvm::ddt(rho_, k_) + fvm::div(phi_, k_) - fvm::laplacian(DkEff(F1), k_) == min(G, c1*betaStar*k_*omega_) - fvm::SuSp(2.0/3.0*rho_*divU, k_) - fvm::Sp(rho_*betaStar*omega_, k_) ); Can you please tell me if someone agrees with me? Regards Cosimo
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Cosimo Bianchini Ergon Research s.r.l. Via Panciatichi, 92 50127 Florence - ITALY Tel: +39 055 0763716 Mob: +39 320 9460153 e-mail: cosimo.bianchini@ergonresearch.it URL: www.ergonresearch.it |
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August 30, 2007, 06:17 |
Yes your are correct, I implem
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#2 |
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Yes your are correct, I implemented the model just before release and didn't have time to test it. I will check it through again, test it and post a corrected version next week sometime.
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August 31, 2007, 10:18 |
Here is a corrected version of
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#3 |
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Here is a corrected version of kOmegaSST.C
kOmegaSST.C to replace the file in OpenFOAM-1.4.1/src/turbulenceModels/compressible/kOmegaSST I have tested the model runs and give sensible results but I have not performed a rigorous validation. |
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September 24, 2007, 06:39 |
Hi Henry,
just another small
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#4 |
Member
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Hi Henry,
just another small doubt about the limiter for mut. I could not download the paper you suggest as reference for this model but the reference paper I used for implementing the kOmegaSST (Heat Transfer Predictions using Advanced Two-Equation Turbulence Models; Wolfgang Vieser, Thomas Esch and Florian Menter; CFX Technical Memorandum: CFX-VAL10/0602, 2002) have a different limiter for mut: mut = rho* a1*k/max(a1*omega,sqrt(2)*mag(symm(gradU)*F2)); The standard release instead is using: mut = rho* a1*k/max(a1*omega,mag(symm(gradU)*F2)); Is it a bug or it is just a correction to make it suitable for heat transfer applications? Please tell me what is your paper saying about that. Thanks a lot Cosimo
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Cosimo Bianchini Ergon Research s.r.l. Via Panciatichi, 92 50127 Florence - ITALY Tel: +39 055 0763716 Mob: +39 320 9460153 e-mail: cosimo.bianchini@ergonresearch.it URL: www.ergonresearch.it |
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September 24, 2007, 06:51 |
All the k-Omega papers I have
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#5 |
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All the k-Omega papers I have give this term without the sqrt(2) but then it could easily be contained in a1. What value is proposed for a1 in CFX-VAL10/0602 and does it differ from the value proposed in the papers on the model?
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September 24, 2007, 07:50 |
I defintely agree with you.
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#6 |
Member
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I defintely agree with you.
My value for a1 is 0.31 so if the two equations are consistent your should be 0.31/sqrt(2) = 0.2192. Thanks for confirming that. Cosimo
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Cosimo Bianchini Ergon Research s.r.l. Via Panciatichi, 92 50127 Florence - ITALY Tel: +39 055 0763716 Mob: +39 320 9460153 e-mail: cosimo.bianchini@ergonresearch.it URL: www.ergonresearch.it |
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September 24, 2007, 07:52 |
Hi,
I am testing the kOmega
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#7 |
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Claus H. Ibsen
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Hi,
I am testing the kOmegaSST model using the above kOmegaSST.C file. I am getting this error messages: --> FOAM FATAL ERROR : incompatible dimensions for operation [omega[1 -3 -2 0 0 0 0] ] - [((rho*((tanh(pow4(min(min(max((((1|betaStar)*sqrt( k))|(omega*y)),((500*(mu|rho) )|(sqr(y)*omega))),(((4*alphaOmega2)*k)|(max((((2* alphaOmega2)*(grad(k)&grad(ome ga)))|omega),1.0e-10)*sqr(y)))),10)))*(gamma1-gamma2))+gamma2))*((2*mut)*(grad(U )&&dev(symm(grad(U))))))[2 -4 -3 0 0 0 0] ]#0 Foam::error::printStack(Foam:stream&) in "/home/ci/OpenFOAM/OpenFOAM-1.4.1/lib/linuxGccDPOpt/libOpenFOAM.so" #1 Foam::error::abort() in "/home/ci/OpenFOAM/OpenFOAM-1.4.1/lib/linuxGccDPOpt/libOpenFOAM.so" #2 void Foam::checkMethod<double>(Foam::fvMatrix<double> const&, Foam::GeometricField<double,> const&, char const*) in "/home/ci/OpenFOAM/OpenFOAM-1.4.1/applications/bin/linuxGccDPOpt/rhoSimpleFoam" #3 Foam::tmp<foam::fvmatrix<double> > Foam::operator-<double>(Foam::tmp<foam::geometricfield<double,> > const&, Foam::tmp<foam::fvmatrix<double> > const&) in "/home/ci/OpenFOAM/OpenFOAM-1.4.1/lib/linuxGccDPOpt/libcompressibleTurbulenceMod els.so" #4 Foam::compressible::turbulenceModels::kOmegaSST::c orrect() in "/home/ci/OpenFOAM/OpenFOAM-1.4.1/lib/linuxGccDPOpt/libcompressibleTurbulenceMod els.so" #5 main in "/home/ci/OpenFOAM/OpenFOAM-1.4.1/applications/bin/linuxGccDPOpt/rhoSimpleFoam" #6 __libc_start_main in "/lib/libc.so.6" #7 Foam::regIOobject::readIfModified() in "/home/ci/OpenFOAM/OpenFOAM-1.4.1/applications/bin/linuxGccDPOpt/rhoSimpleFoam" From function checkMethod(const fvMatrix<type>&, const GeometricField<type,>&) in file /home/dm2/henry/OpenFOAM/OpenFOAM-1.4.1/src/finiteVolume/lnInclude/fvMatrix.C at line 1232. FOAM aborting Is that an error in my setup of the case, or is the error in the kOmegaSST.C file? Thanks, Claus. |
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September 24, 2007, 08:56 |
The value of a1 in the papers
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#8 |
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The value of a1 in the papers I have is also 0.31. I don't know at what point Menter added the sqrt(2) prefactor I haven't seen it in any of the published papers on the k-Omega model I have but I don't have a full set.
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September 24, 2007, 11:16 |
Hi Claus!
I would guess tha
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#9 |
Assistant Moderator
Bernhard Gschaider
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Hi Claus!
I would guess that the problem is with the setup. One common problem is that people take a k-eps-case, rename the epsilon-file to omega but don't change the dimensions (although that would not explain the difference in dimensions in your case). Check the dimensions Bernhard
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September 24, 2007, 11:54 |
Hi Weller,
I also have got a
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#10 |
Member
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Hi Weller,
I also have got an article without the sqrt(2): Menter, Two Equation Eddy-Viscosity Turbulence Models for Engineering Applications, AIAA Journal Vol.32 , N 8, 1994. In that case however: mut = rho* a1*k/max(a1*omega,mag(OMEGA)*F2)); with OMEGA = absolute value of vorticity = mag(curl(U)) != strain rate magnitude = 0.5*(grad(U) + grad(U).T). Could this be the mistake? Am I misunderstanding anything? Regards Cosimo
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Cosimo Bianchini Ergon Research s.r.l. Via Panciatichi, 92 50127 Florence - ITALY Tel: +39 055 0763716 Mob: +39 320 9460153 e-mail: cosimo.bianchini@ergonresearch.it URL: www.ergonresearch.it |
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September 24, 2007, 12:03 |
It is not a mistake, the model
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#11 |
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It is not a mistake, the model has evolved over the years particularly in this term. I assure your that what I have implemented is what is in the paper I refer to in the header. I cannot say if the form you are referring to is preferable to the form I have implemented as I do not have all the relevant literature on the subject.
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September 24, 2007, 12:44 |
You are right: there are sever
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#12 |
Member
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You are right: there are several different versions of such model. I do not have all the papers as well but, as far as I can see, your version is actually the same model implemented in CFX 10.
Thanks for this clarification, Cosimo
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Cosimo Bianchini Ergon Research s.r.l. Via Panciatichi, 92 50127 Florence - ITALY Tel: +39 055 0763716 Mob: +39 320 9460153 e-mail: cosimo.bianchini@ergonresearch.it URL: www.ergonresearch.it |
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September 25, 2007, 05:48 |
I forgot to wmake... everythin
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#13 |
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Claus H. Ibsen
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I forgot to wmake... everything is working nice now.
Sorry for the inconvenience. Claus. |
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January 21, 2009, 09:55 |
Could somebody please supply m
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#14 |
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Andrew Parker
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Could somebody please supply me with an electronic copy of: Heat Transfer Predictions using Advanced Two-Equation Turbulence Models; Wolfgang Vieser, Thomas Esch and Florian Menter; CFX Technical Memorandum: CFX-VAL10/0602, 2002
I understand this explains the automatic wall function treatment for the SST model, I would appreciate any papers which discuss this, not just the above. The only reference I can find is in Menter's Ten years of industrial experiance with the SST model, ref [8], but I can't seem to find the paper anywhere?? Any help would be appreciated. Cheers, Andy |
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November 13, 2009, 23:59 |
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#15 |
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Mahwish
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I have the same problem .I want to know how SSt handels low Re number flows
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November 14, 2009, 05:19 |
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#16 |
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The k-omega-SST model I implemented is the high-Re form to be used with the standard, continuous/adaptive or rough wall-functions supplied. However it would be quite easy to implement the low-Re form of the model as this simply requires the application of damping functions on a few terms.
H |
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November 14, 2009, 13:23 |
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#17 |
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Fabian Braennstroem
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As I understood it, the current implemented SST model is suitable for low-re flows as well. Though one needs different wall treatment (especially for omega). And maybe the use of some damping functions is better. Do you have any experience in it?
Fabian |
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November 14, 2009, 14:25 |
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#18 |
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The k-omega-SST model we currently release is based on a blend of the high-Re k-epsilon and k-omega models, not the low Re k-omega model. With an adaptive/continuous wall-function you can use this model to resolve the near-wall low-Re flow with some degree of accuracy but if you want to resolve these details accurately you will need to include the low-Re damping-functions into the k-omega part of the model and use a mesh with adequate resolution in the near-wall region.
H |
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November 14, 2009, 14:44 |
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#19 |
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Fabian Braennstroem
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Thanks for the explanation!
Fabian |
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November 15, 2009, 17:12 |
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#20 |
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Mahwish
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Thanks a lot .
But by solving right to the wall will be espensive right that's why we avoid that .Rather than using wall functions will be a cheap alternative. I don't know what CFX using as a standard SST model . |
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