CFD Online Logo CFD Online URL
www.cfd-online.com
[Sponsors]
Home > Forums > OpenFOAM Running, Solving & CFD

SimpleFoam nutilda an R

Register Blogs Members List Search Today's Posts Mark Forums Read

Like Tree3Likes
  • 2 Post By markusrehm
  • 1 Post By Tobi

Reply
 
LinkBack Thread Tools Display Modes
Old   May 26, 2008, 04:41
Default SimpleFoam nutilda an R
  #1
Senior Member
 
linnemann's Avatar
 
Niels Nielsen
Join Date: Mar 2009
Location: NJ - Denmark
Posts: 450
Rep Power: 15
linnemann will become famous soon enough
What are nutilda and R for when solving using simpleFoam?
__________________
Linnemann

PS. I do not do personal support, so please post in the forums.
linnemann is offline   Reply With Quote

Old   May 26, 2008, 04:52
Default nuTilda is the kinematic turbu
  #2
New Member
 
Daniela
Join Date: Mar 2009
Location: Italy
Posts: 4
Rep Power: 8
danie is on a distinguished road
nuTilda is the kinematic turbulent viscosity
danie is offline   Reply With Quote

Old   May 26, 2008, 05:12
Default and R is the Reynolds Stress t
  #3
ngj
Senior Member
 
Niels Gjoel Jacobsen
Join Date: Mar 2009
Location: Deltares, Delft, The Netherlands
Posts: 1,607
Rep Power: 25
ngj will become famous soon enoughngj will become famous soon enough
and R is the Reynolds Stress tensor.

Best regards,

Niels
__________________
Please note that I do not use the Friend-feature, so do not be offended, if I do not accept a request.
ngj is offline   Reply With Quote

Old   May 26, 2008, 07:18
Default Hey thanks for the quick reply
  #4
Senior Member
 
linnemann's Avatar
 
Niels Nielsen
Join Date: Mar 2009
Location: NJ - Denmark
Posts: 450
Rep Power: 15
linnemann will become famous soon enough
Hey thanks for the quick reply :-)
__________________
Linnemann

PS. I do not do personal support, so please post in the forums.
linnemann is offline   Reply With Quote

Old   May 26, 2008, 16:30
Default Hi everybody! concerning R
  #5
Member
 
Leonardo Nettis
Join Date: Mar 2009
Posts: 72
Rep Power: 8
dinonettis is on a distinguished road
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
dinonettis is offline   Reply With Quote

Old   August 17, 2008, 10:55
Default Hi, I am running a k-eps
  #6
Member
 
Ivan Lau
Join Date: Mar 2009
Location: Hong Kong
Posts: 56
Rep Power: 8
ivanwhlau is on a distinguished road
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
ivanwhlau is offline   Reply With Quote

Old   August 17, 2008, 11:07
Default Hi, all, In regards to bo
  #7
Member
 
Ivan Lau
Join Date: Mar 2009
Location: Hong Kong
Posts: 56
Rep Power: 8
ivanwhlau is on a distinguished road
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
ivanwhlau is offline   Reply With Quote

Old   August 18, 2008, 05:57
Default You only have to set the field
  #8
Senior Member
 
Eugene de Villiers
Join Date: Mar 2009
Posts: 725
Rep Power: 12
eugene is on a distinguished road
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.
eugene is offline   Reply With Quote

Old   August 18, 2008, 06:14
Default Thanks a lot, Eugene.
  #9
Member
 
Ivan Lau
Join Date: Mar 2009
Location: Hong Kong
Posts: 56
Rep Power: 8
ivanwhlau is on a distinguished road
Thanks a lot, Eugene.
ivanwhlau is offline   Reply With Quote

Old   March 9, 2009, 06:44
Default Hi openfomers, I am trying to
  #10
New Member
 
Gerard Mouokue
Join Date: Mar 2009
Location: Darmstadt, Hessen, Germany
Posts: 16
Rep Power: 8
gerado is on a distinguished road
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
gerado is offline   Reply With Quote

Old   March 13, 2009, 06:22
Default HI Gerard, I dont know the
  #11
Senior Member
 
Rishi .
Join Date: Mar 2009
Posts: 140
Rep Power: 8
hellorishi is on a distinguished road
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
hellorishi is offline   Reply With Quote

Old   January 18, 2011, 04:08
Default
  #12
Senior Member
 
Markus Rehm
Join Date: Mar 2009
Location: Erlangen (Germany)
Posts: 176
Rep Power: 8
markusrehm is on a distinguished road
Hello,

an answer is given here

nut and nuTilda

Markus
palmerlee and chengyu like this.
markusrehm is offline   Reply With Quote

Old   October 8, 2014, 12:14
Default
  #13
New Member
 
Altan
Join Date: Apr 2011
Posts: 12
Rep Power: 6
alyucel is on a distinguished road
Quote:
Originally Posted by dinonettis View Post
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
i'am wondering too

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?
alyucel is offline   Reply With Quote

Old   October 9, 2014, 08:14
Default
  #14
Senior Member
 
Tobi's Avatar
 
Tobias Holzmann
Join Date: Oct 2010
Location: Leoben (Austria)
Posts: 1,086
Blog Entries: 6
Rep Power: 19
Tobi will become famous soon enough
Send a message via ICQ to Tobi Send a message via Skype™ to Tobi
Hello,

  • nut is not necessary to declar if you want standard settings. OpenFOAM sets up your nuTilda -> nut itselfs and you will get this field in every saved iteration step.
  • R is not necessary anymore


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()
        )
    );
}
vaina74 likes this.
__________________
Best regards,
Tobias Holzmann

Some interesting OpenFOAM tutorials and videos on www.Holzmann-cfd.de
Tobi is offline   Reply With Quote

Reply

Thread Tools
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are On
Pingbacks are On
Refbacks are On


Similar Threads
Thread Thread Starter Forum Replies Last Post
Problems with the RSM in simpleFoam sberg OpenFOAM Running, Solving & CFD 10 February 25, 2014 20:39
What is phi in simpleFoam ehsan_vaghefi OpenFOAM Running, Solving & CFD 7 September 29, 2013 11:00
Using simpleFoam with water nico765 OpenFOAM Running, Solving & CFD 7 October 23, 2007 05:39
SimpleFoam woes msrinath80 OpenFOAM Bugs 2 April 13, 2007 10:15
What does the variables R and nuTilda represent in the icofoam ztdep OpenFOAM Running, Solving & CFD 2 August 18, 2005 22:21


All times are GMT -4. The time now is 16:48.