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February 12, 2011, 09:08 
komega SST

#61 
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Giannis Asproulias
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Hi OpenFOAMers,
Could anyone, please, send me the paper for the compressible komega SST, Sandy, Henry?. Additionally, for which y+ does this model work, meaning the applicability of the used wall function. Menter, F., Esch, T. "Elements of Industrial Heat Transfer Prediction" 16th Brazilian Congress of Mechanical Engineering (COBEM), Nov. 2001 Thanks, giannis i.asproulias@gmail.com 

February 17, 2011, 04:15 

#62  
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BastiL
Join Date: Mar 2009
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Quote:
I am also wondering about that. Henry mentioned in his posts above ( #54, #56) that one has to use mutLowReWallFunction in case you use a LowRe model but you do not have y+<1 at this specific wall. Otherwise, if you have y+<1 you have to use "no" wall function  but howe to define this in 0/nut?. I am also wondering how to define the value sin k/epsilon/omegaFiles. Regarding komega SST it seems to me like you can not use this approach at all since it is a HiRe model... 

February 17, 2011, 04:37 

#63  
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Quote:
If you have y+ < 1, then k > fixedValue, very small (1e9) Omega > omegaWallFunction (is not really a wall function, is the b.c. defined by Menter for Omega, it works at all y+ I suppose). mut > fixedValue, very small (1e9) If you have y+ > 30, then classical wall function setup If you have 1 < y+ < 30, then k > zeroGradient Omega > omegaWallFunction mut > mutSpalartAllmarasWallFunction (is a kind of all y+ mut wall function, sometime ago Henry said that this should be renamed in mutSpaldingWallFunction...) Hope this can help... Btw, is someone working on transition model for SST? 

February 17, 2011, 19:58 

#64 
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Alexandre Rubel
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Hi everyone, this thread is very intersting. I just wonder one thing, I'm using OF1.6 and I use nut in my 0 file is it mut or nut ?
Last edited by alex_rubel; February 21, 2011 at 01:49. 

February 21, 2011, 10:17 

#65 
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Giannis Asproulias
Join Date: Jan 2011
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Thanks guys for the replies. I was thinking to switch off the wall functions, which are used automatically for every turbulence model in 1.6v (I don't know about 1.7v) and apply manually the BC for the turbulent quantities. This is because I have y+<1 everywhere. Thanks again
Giannis 

April 5, 2011, 04:33 

#66  
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Arne Stahlmann
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Quote:
... I also posted this question here in more details. Arne 

June 6, 2011, 16:08 

#67  
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Martin
Join Date: Jun 2009
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Quote:
what is the reason, that for the zeroGradient BC of k. Why is it not kRWallFunction? Please see also the post under the following link: http://www.openfoam.com/mantisbt/view.php?id=179 What is correct? Martin 

September 21, 2011, 02:18 
Reg:: Subdomain as porous medium

#68 
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Arun raj.S
Join Date: Jul 2011
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Hi Guys,
First very sry to disturb u people...Bt I need some important help I have a created a domain as Domain1 which is Fluid domain Now I want to create a subdomain for Domain1 which is a porous domain Is it possible to create like this? If so can u explain how? 

November 2, 2011, 13:34 

#69  
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Juanito
Join Date: Oct 2010
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Quote:
In order to know the y+ when the grid is in the laminar region (LowRe model, no wall function or nutLowReWallFunciton if y+>1), is it possible to employ the yPlusRAS utility provided by OpenFOAM? or it calculates the y*. It is not cleary explained in other topics like this: http://www.cfdonline.com/Forums/ope...tml#post306730 Thank you very much in advance 

August 23, 2012, 18:07 

#70  
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dw
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Quote:
Dear all, I've been testing the "hybrid" or "enhanced" or "automatic" wall treatment. One thing I found nutSpaldingWallFunction is said to be a continuous WF, however, I cant get a good result with it. I am wondering anyone of you have success with nutSpaldingWallFunction? Model: kwsst Test cases: channelflow, periodic hills. I set omega as omegaWallFunction, k as kqRwallFunction, nut as nutSpaldingWallFunction. And the results are not good. Separation and reattachments pts are all not good. Another question is that, in Menter's paper of improved wall treatment, it is clear that omega is written as sqrt(sqr(omega_vis)+sqr(omega_log)). But in OF2.0, the utau is calculated with sqrt(k), is this correct? And also I am wondering why do we need a nut wall function, since the nut can be calculated simply by k and omega, once we have omega already set with certain wall function, then nut is calculated, why need nut wall function then? Thanks! 

March 4, 2013, 17:05 

#71  
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Teng Wu
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Quote:
Have you got the paper "Elements of Industrial Heat Transfer Prediction"? If so, could you kindly send a copy to me? tengwu86@gmail.com Thanks, 

March 4, 2013, 17:07 

#72  
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Teng Wu
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Quote:
Could you kindly send a copy of the paper "Elements of Industrial Heat Transfer Prediction" to me? tengwu86@gmail.com Thanks, 

March 11, 2013, 07:37 

#73  
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Dogan
Join Date: Nov 2012
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Quote:
i would like to ask a question about the nutUSpaldingWallFunction. I have used this wall function in a diffusor test case with kOmegaSST turbulence model, and i also made the same simulation with CFX, then i compared the results. since i know, CFX is using the so called automatic wall treatment, i would like to be sure about that if nutUSpaldingWallFunction is also an automatic wall treatment, or in OpenFOAM is there anouther way to make an automatic wall treatment? Thanks 

November 5, 2013, 12:28 
Compressible kOmegaSST BCs

#74 
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Claudio
Join Date: Mar 2012
Location: Milano, Italy
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Hi foamers!
I find this old thread, very interesting for me in this moment, but I still can't find an answer to my problem... Here there is a description of my case (it is 3D). I have my geometry inside a box, but its faces (of the box) must be considered as patches, not as walls. The fluid moves from the right to the left. The flow comes from the pipe on the right, but also from the opening on high. The picture attached is a slice (coming from the laminar case). To have an idea about the dimensions, the pipe on the right side has D=0.0025 m. Now my problem: which BCs I have to put for the simulation?! Of course, as wrote in the title, the case is compressible. I used, for a first attempt, wall functions for the geometry (for all k, omega, alphat and mut); then, I'm not sure about which could be right BCs on 1) the "external" faces (of the box) 2) the inlet (that of the pipe), "ingressoOX" in the folder I put "fixedValue" on both. Maybe, could I use  "turbulentMixingLengthFrequencyInlet" for omega  "turbulentIntensityKineticEnergyInlet" for k on inlet ("ingressoOX") patch? No problem for the outlet of the geometry, on the left side, because it is "free"... Moreover, have the values I used any sense? or which values should I use?! I attach also a folder with these BCs I used for now. Thank you in advance for your suggestions! Best regards, Claudio PS: I'm using rhoSimplecFoam as solver 

March 13, 2014, 20:08 
kOmegaSST for developed channel flow

#75 
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Manan
Join Date: Oct 2013
Location: Göteborg
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HI henry
I needed a little help. I am trying to adapt kOmegaSST model to kOmegaSST EARSM model and wish to show its performance for simple developed channel flow, to begin with. To get on this track, I first thought about testing kOmegaSST for channel flow and seeing if the results I get compare well with what other researchers have found. Here's the thread that talks about my attempts: http://www.cfdonline.com/Forums/ope...nnelflow.html I know that you implemented kOmegaSST in openFoam and hence wanted to ask you if you ever validated it for channel flow and if yes, would you mind sharing the case files. Have been stuck on this for a little while and don't really know whom to ask. Any help is appreciated. Thanks. 

February 11, 2016, 14:55 

#76 
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Hi everyone!
A very interesting is this topic! I have also some questions of my own regarding the komega SST model... yes, one more Foamer who is left in the doubts.. ^^ To sum up quickly, as I lacked theoritical background in CFD (I am relatively new in this field), I started to investigate more about the whole process which is behind all CFD Simulations. Now, I'm putting a lot of interests in the turbulence models (mainly k epsilon, k omega and also k omega SST). I want to link the formula that we can read in the litterature with the actual formula used in the OpenFOAM source code. My biggest doubt lies on the k omega sst model. My "theoritical" sources about the k omega sst formulation and its representation in PDE come from :
Now my questions :
Code:
arg1 = min ( max(term 1); term 2 ) Code:
arg1 = min [ min ( max(term 1); term 2 ) ; 10 ]
Have a nice evening, I'm looking forward to read your answers! 

February 12, 2016, 04:50 

#77 
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Join Date: Aug 2015
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Hi again!
I forget to mention that I was using OpenFOAM 2.0.x. I rethink of that this morning, about the Code:
arg1 = min ( term 1 ; 10 ) EDIT: About the modelling of the k omega SST formulation in a compressible case: I guess the term with a factor "2/3" on the RHS of the PDE comes from the formulation of the Boussinesq Approximation in a compressible case (2nd term): Does anyone could confirm or infirm my thoughts ? Thanks in advance! 

November 24, 2016, 23:04 

#78  
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Location: Singapore
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Quote:
You are right about the "2/3" term. It indeed comes from Boussinesq's eddy viscosity hypothesis. The point is that we are replacing the Reynolds stress tensor with a model but we still want to enforce that the trace of the tensor remains at . Since the first part of the model is deviatoric (traceless), the enforcement must come from the second term. But note that this assumes that the turbulence is homogeneous, i.e. . Now to my problem. I share the same concerns about the appearance of the limiting constants in 'arg1' and 'arg2'. Also, I found some inconsistencies in the 'omegaEqn' and 'kEqn' as well. I have modified the current kOmegaSST model (OF2.4.0) to match with what has been given in Menter's paper exactly. I would like to know if anybody has a good validation case, such as compressible pipe flow or Couette flow, which I can use to test the model. USV 

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