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February 8, 2017, 11:13 

#21  
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Ricardo Ferreira
Join Date: May 2015
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Quote:
In fact, simulations without wall functions you should keep y+ close unity. Try use "nutLowReWallFunction" in type of nut boundary condition in wall regions. In inlet you can use "calculated" type. Take especial attention to set wall BC in k/epsilon/omega Dict files. Use kLowReWallFunction, epsilonLowReWallFunction, omegaWallFunction, respectively, for wall BCs for k, epsilon and omega dict files. For inlet BC type i used turbulentIntensityKineticEnergyInlet, turbulentMixingLengthDissipationRateInlet, turbulentMixingLengthFrequencyInlet for k, epsilon and omega, respectively. If something is not clear let me know. Cheers. 

February 8, 2017, 11:47 

#22  
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Fredi Cenci
Join Date: Dec 2016
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Quote:
So, on walls where I do NOT want to use wall functions (y+<1) I should set LowReWallFunction instead fixedValue? best regards, 

February 8, 2017, 13:43 

#23 
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Ricardo Ferreira
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Yes. As far as I know, this type of BC allows integration up to wall. Besides, it can be used if you use wall functions too (it is automatic, you can use with or without wall functions). Therefore, who determines whether it will be or not integrated up to the wall is nut BC. Resuming, if you use a Low Reynolds Number Turb. Model to calculate nut you should use the same type of BC based on Low Reynolds for k and epsilon. Evidently, the models that use omega are already built in the concept of Low Reynolds models, so there is no Low Re in yours BC denominations (notice the name of BC: "omegaWallFunction").


February 8, 2017, 14:27 

#24  
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Fredi Cenci
Join Date: Dec 2016
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Quote:
Now I changed to epsilonLowReWallFunction; kLowReWallFunction; and nutLowReWallFunction with values of the internalField.. seems like it is converging.. thanks a lot! Best Regards, 

May 9, 2017, 01:53 

#25 
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AmolG
Join Date: Apr 2017
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Dear William,
What did you get after using komega SST model with low Reynolds Number correction? Regards! Amol 

August 10, 2017, 09:35 

#26 
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Vino
Join Date: Mar 2013
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Dear fredicenci,
Are you able to solve kepsilon or any other model with out wall function (y+<1). My simulation shoots up without wall function. thank you. 

August 10, 2017, 11:36 

#27 
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Fredi Cenci
Join Date: Dec 2016
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Yes. You can use lowReynolds wall functions.
Another alternative is to set the values of k,and omega (or epsilon) on the wall. In this case you should use fixedValue. best, Fredi Cenci 

August 11, 2017, 15:41 

#28 
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Vino
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November 5, 2017, 22:40 

#29 
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Harshal Akolekar
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Great! Great!


February 17, 2018, 11:25 
selection of Turbulence model

#30 
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Syed Waqar Mehdi
Join Date: Mar 2016
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Hello
I am currently doing a project regarding analysis on airfoil of Vertical axis wind turbine , I have already researched about many turbulence models like realizable Kepsilon , RNG KEpsilon, spalart allmaras and KOmega SST but which should i select and on what basis. Please help me about this 

February 17, 2018, 11:53 
selection of Turbulence model

#31 
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Syed Waqar Mehdi
Join Date: Mar 2016
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Hello
I am currently doing a project regarding analysis on airfoil of Vertical axis wind turbine , I have already researched about many turbulence models like realizable Kepsilon , RNG KEpsilon, spalart allmaras and KOmega SST but which should i select and on what basis. Please help me about this regards Waqar Mehdi shahwaqar36@gmail.com 

September 9, 2018, 18:44 

#32  
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Federico Agustín Caccia
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Quote:


November 6, 2018, 04:13 
Menter's SST komega turbulent model

#33 
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Nina Philipova
Join Date: Jul 2012
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Dear Users of ANSYS Fluent,
I have to apply Menter's SST komega turbulent model in Fluent for simulating wall bounded tortuous channel. I looked through Fluent User's Guide and Menter's publications: Menter, F. R. (1994), "TwoEquation EddyViscosity Turbulence Models for Engineering Applications", AIAA Journal, vol. 32, no 8. pp. 15981605 Menter, F, Kuntz, M., Laugtry, R., Ten years of industrial experience with SST Turbulence model ,Turbulence, Heat and Mass Transfer 4. The cited constants in Fluent User's Guide are different from those in Menter' publications and the sites of NASA, Wikipedia. Could some one help me which constant I have to use? I will be grateful to you so much! 

November 6, 2018, 07:21 
Menter's SST komega turbulent model

#34 
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Nina Philipova
Join Date: Jul 2012
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Constants are the same. Fluent constants are reciprocal to the constants in Menter's publications


December 16, 2018, 10:16 

#35 
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Lee JP
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March 21, 2019, 04:56 

#36  
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ahmed
Join Date: Jan 2016
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Quote:
As u referred to DES model, LES is quite computationally expensive compared to any RANS model. It depends on your problem and also depends on the degree of accuracy which you want to achieve. Even LES needs a turbulence model to be used. For some problem LES might take the solver few weeks to be solved, Actually few weeks definitely accepted compared to its fantastic results and its time saving compared to DNS solvers ofc. However, RANS are widely used as most of industrial proposes are not interested in the deep details of the flow fluctuations so they prefer to averaging the flow properties. 

March 21, 2019, 05:13 

#37 
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ahmed
Join Date: Jan 2016
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Hello there,
With respect to ur question, it depends on your application and i highly recommend you to read Klaus A. Hoffmann, Computational Fluid Dynamics Vol. III from page 54 to 65, just 11 pages. In brief, I quick read a presentation before for a prof in some college, i really can't remember it, in which he recommended to use kepsilon models for freeshear layer flows, external flows, small pressure gradient flow. While the komega model are better for internal flows and near wall behavior. SST komega merges the advantages of the two previous models. However the computational cost increases with using Spalart Allmaras model, St. Kepsilon, RNG kepsi, Realizable kepsi, Standard komega, SST komega models, respectively. Although it is recommended to use two or more models on the same application and compare their results so that u can be sure that the model which u chose is gonna work. 

June 24, 2019, 10:08 

#38  
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abdo
Join Date: Apr 2018
Posts: 42
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Quote:
hello brother I'am simulate the swirl flow and I have many problem.. could you help me? 

September 17, 2019, 03:05 
kw (wicox, BSL, SST) Vs. ke

#39 
Member

Here are some takes from my blog posts about the two families of turbulence models:
kw: https://cfdisraelblog.wordpress.com/...%89sstmodel/ ke: https://cfdisraelblog.wordpress.com/...odel%ef%81%a5/ And also the subject of walltreatment, which is of most importance in it of itself: https://cfdisraelblog.wordpress.com/...ansysfluent/ 

March 19, 2020, 18:27 

#40 
Member

I love turbulence. Knowing how to model it in just the right fidelity is an art imho. An art I fell in love with 💕
The intention of this set of posts is to embark on a journey of connecting the dots between CFD and turbulence modeling with the phenomenological and practical concepts of engineering turbulence… Even though it will by no means be all encompassing nor highly accurate I hope for the essence to be captured, and even more so communicated… ✨ https://allaboutcfdtomers.blog/2020/...caneatmenu/ 

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