low reynolds number Kepsilon model
Dear
I need to know which turbulence model in Fluent is equivalent to the low Reynolds number Kepsilon model available in StarCD. I appreciate your answer and I'm looking forward for your reply. Thanks a lot. 
The below mentioned models are the low reynolds number k e models available in Fluent. I am not sure which one used in Star  CD since I never used it. Hope this may give some information.
Index Model 0 Abid 1 LamBremhorst 2 LaunderSharma 3 YangShih 4 AbeKondohNagano 5 ChangHsiehChen Cheers, Alagesanj 
Thanks a lot
Dear Alagesanj
Thank you very much for your your reply I'm doing my simulation using Fluent 6.3 and I have found just three types of Kepsilon models as follow 1 standard 2 RNG 3 Realizable May you tell me how to choose any of the Reynolds number you mentioned. Thanks a lot Quote:

The lowRe models mentioned by Algesanj are only available from the text interface and can not be selected via the gui. If I remember correctly you need to select "turbulence expert" or something like that in the text interface to display these models. The manual for starcd should give the name of the model they use. I would still recommend you to use the twolayer Wolfstein model that is selectable through the gui (extended wall treatment it used to be called I think, I'm not using Fluent that much these days so things might have changed). Of the lowRe models I would recommend the YangShih model.

Hi Amar,
What Jonas mentioned is correct. These low re ke models I mentioned are not available from the GUI. I am thankful to Mr. Jonas since I got to know some very important CFD basics from his previous (very old) posts. Even this low re ke models also I came to know from his post only. After you select the ke model in the GUI you can access the low re ke models by typing define/models/viscous/turbulenceexpert/lowreke then enter. When the command prompt asks for "Enable the lowRe kepsilon turbulence model? [no]" type 'yes'. Now you can see the low re ke model in your GUI. then again type define/models/viscous/turbulenceexpert/lowrekeindex you will be prompted to enter the index number the index number represents the corresponding low re ke model which i have mentioned in my previous post. Hope this will help. Cheers, Alagesan. 
Thanks for those nice words Alagesan. Did you make any comparison between the lowRe models available in Fluent? Which one would you choose as your first alternative?

Hello
I'd like to thank mister Jonas and Alagesan for their help and quick answers of my question, I really thankful. I'm now testing the second model (index1) but I didn't get good results. Actually I also need to know how to do energy unbalance test. Thanks a lot . 
Quote:
I've just read your mails and was happy to find them : i've found an example of the use of fluent in lowreynolds here : http://www.sciencedirect.com/science...14f24c7a85341e it can interest you ? 
Dear Laurence Wallian
Thank you very much for your reply, sure this paper will help me. Also I'd like to ask you if you know how to calculate or do the energy balance test. 
hello,
I'm sorry, but I don't what is the "energy balance test" I hope someone can reply you 
my suggestion
hello amar,
using any one of the low reynolds' number turbulence model from the TUI is ok, but it would be better if you can modify the low reynolds komega model itself. at one time, i had worked on it. but of course, it all depends what and why you want it. best regards, rr123 
Thanks
Dear
Thanks a lot for your reply. What do you mean by modify the low Reynold number and how, please? I appreciate your help. 
komega model
Both k omega models (std and sst) are available as lowReynoldsnumber models as well as highReynoldsnumber models.
The wall boundary conditions for the k equation in the k omega models are treated in the same way as the k equation is treated when enhanced wall treatments are used with the k epsilon models. In my opinion, the Launder and Sharma etc. low Re turb. models essentially linear whereas this low Re komega model is nonlinear. you can model transitional flows better with this komega model. A good paper on komega model is: "A half century historical review of the komega model" basically, you need to know what is your nature of the problem. if you have need to have transitonal behaviour, you can check both the lowRe kepsilon and komega models. best wishes. 
Dear rana
I really thankful for your answers and your interest to solve my problem. May I continue send questions to you because I'm new in using Fluent just two months ago and I need to solve my simulation as soon as possible. Thanks a lot 
ok amar, ask me.
if you have too confidential queries, you may also contact me confidentially. my mail id is royrana123@yahoo.com i will try my bnest to help you. thanks. 
Hi Rana,
I just want to clarify some doubts regarding the low re k w model. My apology to Amar since I am intruding in his thread. I am analysing a 2D airfoil flow at low reynolds number i.e. around 0.1 million to 0.5 million. I used both ke and kw models. SST kw model with transitional flow (low re kw model) performed better than the ke models available in the GUI. But it often failed to predit the transition of laminar to turbulence and drag result shows errror of around 20 to 30%. So finally i used forced transition model and again it was very difficult to get a converged solution. You have mentioned that by modifying the low re kw model itself can give better results. If it is possible can you guide me on this part. Thanks, Alagesan. 
yes, probably i can help in this case.
send me a mail so that i can send you the thesis. thanks and regards. 
Hi,
I am modeling a single phase flow is a circular tube, where the Reynolds number is between 10006000, and I am looking for a single turbulence model capable to predict the shear stress accurately in laminar, transition and turbulent regime compared to theoretical equations. So I wonder if you have any suggestion in using a particular lowRe kepsilon turbulent model, or komega and which will be the best performing model. Thanks for the help. 
thank you very much for your guidance, it works:)

Quote:
THANK YOU VERY MUCH Alagesanj FOR YOUR ORIENTATION 
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