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-   -   Low-Reynolds k-eps models (http://www.cfd-online.com/Forums/fluent/85127-low-reynolds-k-eps-models.html)

p_agoodboy February 17, 2011 21:46

Low-Reynolds k-eps models
 
Hi everybody,

Anybody knows if it is possible to use low-Reynolds k-eps models in Fluent?
To clarify, in low_Re models the coefficients C_mu, C_eps1 and C_eps2 are modified based on flow characteristics or the distance from wall (different approaches in different models), and two source terms are also added to k and eps transport equations.
To summarize, I wanna know if it is possible to employ user defined coefficients rather than constant ones in Fluent and add new terms to the turbulence transport equations.

alastormoody11 February 18, 2011 00:48

Hi,

you can change the constants used for the k-e model using a journal file if you want after each time step or iterations if you want. To get the basic framework you can record a journal file where manually change the constats. Using this as a reference you can add your own functions to the code to change it between time steps.

I do not think that you can add source terms to the existing equations though.

If it is a low- Re flow you could also use the k-w model.

p_agoodboy February 18, 2011 20:48

Thank you for your help.
Could you please give me more explanation about journal files? or tell me where can I obtain more info.
In fact, I should decide whether Fluent is capable enough for my problem or I better proceed to an in-house code. It is actually a determining step for my PhD thesis.
How much using a journal file can increase computational cost? (I mean solution time)
I should model a rather complicated mixed convection turbulence flow and I need to examine different turbulence models so it is important for me to have enough freedom in using software.

p_agoodboy February 18, 2011 21:05

I should add that the coefficients are functions of position too, so it is not enough to change them in each time step but in each cell.


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