LRR(Launder-Reece-Rodi RSTM) turbulent model
 

Dear Foamers,
I want use LRR turbulent model but i didn't find any sample in tutorial files.
I don't know how is its properties which should be set.
Any suggestion will be appreciated.
Best,

any success
 

Hej,

did you have any success?

Hi,
I used tut files which were k-e. their settings are almost the same. you need to change turbulentProperties from k-e to LRR.

missing field R
 

what is the field R that the calculation requires?

R is reynolds stress tensor. i set it zero fixedValue for inlets, zeroGradient for outlets.
i used kqRWallFunction for walls. i am not sure about this one.

thank you very much, I will try this and come back to this here when I have a result.

it seems to work with those boundary conditions, givig approximately the same results as the non-reynolds stress models. the results are slightly improved over the standard k-epsilon

I have same problem. i don't know why its result is approximately same as k-e!

Any idea?

Refer to Literature
 

Dear Maysam,

Kindly refer to the RSM Assessment, Disadvantages in Versteeg & Malalasekara "Introduction to CFD", where it has been mentioned.

:confused:"In some flows RSM performs just as poorly as k-epsilon model ":confused:
--
BTK

Lrr
 

I used to LRR in cyclone, so it had showed better results than k-eps both k-omega models.

I think it's a good model for special cases.

LRR CASE FILE - Reg
 

Dear skeptik,

Thats good to hear.

If you don`t mind, can you upload your LRR case in zipped format for reference.

I am using LRR for Jet flows and I am finding difficulty in convergence and some other problems. So it would be helpful if I go through some converged cases. By that hope I can figure out what is going wrong in my simulations.

Thanks in advance.
--
KANNAN

Hi maysmech,

The evaluation of the turbulence model is not that straightforward!

Mesh resolution and wall modelling strategy is quite critical for the conclusions of the simulations results. In any case, if there is no high strain in your flow, I cannot see the advantage of using a highly expensive turbulence model like RSM. For a large number of applications, the isotropic assumption is fair enough.

Regards,

Here you can download cyclone- testcase

LRR axisymmetric jet
 

Dear Skeptik,
I used almost the same conditions as you used, but for axisymmetric jet case i am finding difficulties in convergence and getting physically possible solutions
--
KANNAN

As i know, it's a common problem of the RSM-models.
But, possibly, bad convergence and non-physically solutions were reasoned by wrong boundary conditions. What is your case? Can you publish it?

Lrr case
 

Dear Skeptik,

Here is the first case which i tried.

http://www.cfd-online.com/Forums/ope...ess-model.html

--
KANNAN

Hi there skeptik,

Thank you very much for you cyclone download, I also wanted to try out LRR for a cyclone so your post was very useful.

I was wondering, did you ever manage to verify the results on your cyclone? I ran your case first with simpleFoam with no turbulence and then with LRR activated. The velocity plot in the z-plane (which Im assuming is the tangential velocity profile?) still appears to be a non Rankine Vortex like this one for K-e.
http://www.waset.org/journals/waset/v59/v59-328.pdf

Whereas I am hoping RSM/LRR looks like this one...which is good enough for what I am currently doing
http://www.cfd.com.au/cfd_conf12/PDFs/040KAR.pdf

What do you think? Any comments appreciated.

Best Regards

Jason

Hi Jason,

About my case. The velosity profile was not correct. But at least RSM results were better than k-eps. Sorry, I can't remember what was right and what was wrong exactly.

My cyclone was just a test-case, i've used third-party mesh. May be problem in initial conditions or in the mesh discretisation. At least about that case i'd say that mesh needs to be refined in near-wall region. For instance by 'refineWallLayer" function. Also as i remember there was tetra-mesh. It could be converted by polyDualMesh which reduces mesh size. Finally i didn't try to change fvSchemes.

Another pic about RSM
 

Here you can see differences.
Vortexes are little bit bigger and have little bit higher frequency. But not so high as in experimental case.

Attachment 26684

Hi again,
Thanks for the reply, I'm testing a snappy mesh with layers but I think the mesh is a little too coarse in the middle for my liking. So, I will build a pure hex mesh similar to the two cited papers and begin again.
BR
Jason

Dear Skeptik,
Any success in axisymmetric jet case using LRR ?
--
KANNAN

About a case
 

Really, i haven't understood your case.
But i have something to say about case settings.

1. You chose steady-state simulation. Do you know that in this case you get only rough solution?

try pisoFoam.

2. You should play with fvSchemes. Higher-order schemes are preferred, but you should balance in numerical stability and numerical scheme.

All I need is just a rough solution i.e. averaged values using steady state RANS LLR
--
KANNAN

Hello friends

I want to implement LLR model in OpenFOAM for micro-jet extracting device . It is asking

me to write R file.I have written that file. After that when I run the code parallaly It produce

floating point error in decomposePardict.

I am attaching you both log file and R file in zip format

Regards
harshawardha

Reynolds Stress Model (for example LRR)
 

My case is a CYCLONE. I want to use Reynolds Stress Model (LRR) at OpenFOAM but I do not know how to use and define at the software.
To begin, I found a file R and changed it. My boundary conditions are inlet, outlet and walls.

File U is as fallow:
dimensions [0 1 -1 0 0 0 0];
internalField uniform (0 0 0);
boundaryField
{
walls
{
type noSlip;
}
inlet
{
type pressureInletOutletVelocity;
value uniform (-10 0 0);
}
outlet
{
type pressureInletOutletVelocity;
value uniform (0 0 0);
}
}

File R is as fallows:
dimensions [0 2 -2 0 0 0 0];
internalField uniform (0 0 0 0 0 0);
boundaryField
{
wallS
{
type kqRWallFunction;
value uniform (0 0 0 0 0 0);
}

inlet
{
type pressureInletOutletVelocity;
value uniform (0.0015325 0 0 0.0015325 0 0.00306504);
}

outlet
{
type zeroGradient;
}
}

According to the file U, What changes do I need on R?
Have you a file R to send to me?
I need the fvSolution and fvSchemes files for model LRR.

--> FOAM FATAL IO ERROR:
Cannot find patchField entry for walls

file: /home/dadehnegar/OpenFOAM/dadehnegar-4.0/run/project/MYcyclone/air+water/rsmLRR/0/R.boundaryField from line 25 to line 37.

According to the files U and R in above, help me to solve this error please.

Thanks
Ali

Dear skeptik,
I can not download your testcase in above. Please send me your CYCLONE case if possible. It will help me very much.

Thanks,
Ali

Dear Skeptik,

I need your help.
Please send me your Email address.

Thanks,
Ali

Dear skeptik
I created R file and corrected it. Now, my problem is at the fvSchemes as fallow:

--> FOAM FATAL IO ERROR:
[0] keyword div(phi,R) is undefined in dictionary "/home/ebtedaei/OpenFOAM/ebtedaei-4.0/run/project/MYcyclone/air+water/rsmLRR/system/fvSchemes.divSchemes"
[0]
[0] file: /home/dadehnegar/OpenFOAM/ebtedaei-4.0/run/project/MYcyclone/air+water/rsmLRR/system/fvSchemes.divSchemes from line 30 to line 35.
[0]


Please send a fvSchemes file for LRR model and your Email address.

Thanks
Ali

lrr simulation
 

Please can you share again the file?

Hi,
can you please upload this file again as it is un available?