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May 26, 2008, 05:41 |
SimpleFoam nutilda an R
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#1 |
Senior Member
Niels Nielsen
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What are nutilda and R for when solving using simpleFoam?
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May 26, 2008, 05:52 |
nuTilda is the kinematic turbu
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#2 |
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Daniela
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nuTilda is the kinematic turbulent viscosity
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May 26, 2008, 06:12 |
and R is the Reynolds Stress t
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#3 |
Senior Member
Niels Gjoel Jacobsen
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and R is the Reynolds Stress tensor.
Best regards, Niels
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May 26, 2008, 08:18 |
Hey thanks for the quick reply
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#4 |
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Niels Nielsen
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Hey thanks for the quick reply :-)
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Linnemann PS. I do not do personal support, so please post in the forums. |
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May 26, 2008, 17:30 |
Hi everybody!
concerning R
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#5 |
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Leonardo Nettis
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Hi everybody!
concerning R and nutilda I would like to know something more as well!! -First of all, should I iniatilize them with a value different from 0?? -Second, in simpleFoam when I use the k-epsilon model I've read on this forum that they are not necessary. Why?? Thank you in advance. dino |
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August 17, 2008, 11:55 |
Hi,
I am running a k-eps
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#6 |
Member
Ivan Lau
Join Date: Mar 2009
Location: Hong Kong
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Hi,
I am running a k-epsilon RNG model (simepleFoam). turbulent, incompressible air flow around a rectangular low rise 3D building I have set the following initial values of inlet: U k=1/2(UI)^2 epsilon=Cmu^0.75*k^1.5/l nuTilda=Cmu&K^2/epsilon (is it correct?) Do I need to set the value of R (currently, zeros)? If so, what should that be? Please kindly advise. Regards, Ivan |
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August 17, 2008, 12:07 |
Hi, all,
In regards to bo
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#7 |
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Ivan Lau
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Location: Hong Kong
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Hi, all,
In regards to boundary conditions, besides inlet, I have the following: outlet, wall, ground, external zeroGradient for every parameters U=0,0,0 at wall & ground p=0 at outlet Should I set k as zero at wall? Re~=10^5 Pleas kindly help. Regards, Ivan |
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August 18, 2008, 06:57 |
You only have to set the field
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#8 |
Senior Member
Eugene de Villiers
Join Date: Mar 2009
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You only have to set the fields used by your solver/model. nuTilda and R are not used by the RNG model. For high-Re models k at the wall is normally set to zero gradient.
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August 18, 2008, 07:14 |
Thanks a lot, Eugene.
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#9 |
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Ivan Lau
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Thanks a lot, Eugene.
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March 9, 2009, 06:44 |
Hi openfomers,
I am trying to
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#10 |
New Member
Gerard Mouokue
Join Date: Mar 2009
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Hi openfomers,
I am trying to understand the implementation of simpleFoam but I have a problem with nuTilda. can someone tell me the difference between nut and nuTilda ? Regards Gerard |
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March 13, 2009, 06:22 |
HI Gerard,
I dont know the
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#11 |
Senior Member
Rishi .
Join Date: Mar 2009
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HI Gerard,
I dont know the details, however I am also interested. Just a clue: check the C++ documentation: http://foam.sourceforge.net/doc/Doxygen/html/incompressible_2kEpsilon_2kEpsilon_ 8C-source.html 00120 nut_(Cmu_*sqr(k_)/(epsilon_ + epsilonSmall_)) and some details... http://foam.sourceforge.net/doc/Doxygen/html/classFoam_1_1incompressible_1_1RASM odel.html Yet to read it completely. Post here if you find answers to your questions. Regards Rishi |
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January 18, 2011, 04:08 |
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#12 |
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Markus Rehm
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October 8, 2014, 13:14 |
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#13 | |
New Member
Altan
Join Date: Apr 2011
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Quote:
Second, in simpleFoam when I use the k-epsilon model I've read on this forum that they are not necessary. Why?? and where is using openFoam R and nuTilda? |
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October 9, 2014, 09:14 |
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#14 |
Super Moderator
Tobias Holzmann
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Hello,
Source code: $FOAM_SRC/turbulenceModel/incompressible/ras/kEpsilon Code:
nut_ ( IOobject ( "nut", runTime_.timeName(), mesh_, IOobject::NO_READ, IOobject::AUTO_WRITE ), autoCreateNut("nut", mesh_) ) Code:
tmp<volSymmTensorField> kEpsilon::R() const { return tmp<volSymmTensorField> ( new volSymmTensorField ( IOobject ( "R", runTime_.timeName(), mesh_, IOobject::NO_READ, IOobject::NO_WRITE ), ((2.0/3.0)*I)*k_ - nut_*twoSymm(fvc::grad(U_)), k_.boundaryField().types() ) ); }
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