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-   -   Turbulence Model L.E.S (http://www.cfd-online.com/Forums/star-ccm/65616-turbulence-model-l-e-s.html)

hamoudi June 21, 2009 06:13

Turbulence Model L.E.S
 
Good Moning Everybody,

Please if every one can answer me, i am doing a simulation in 2D
Can i use L.E.S as a turbulence Model in 2D simulation
because L.E.S turbulence model is very robust

Thank you in advance

Maddin June 22, 2009 07:31

You can but sure that you want this?!

vishyaroon June 23, 2009 10:53

If you talk to people who work with LES, they will frown if you call it a model, because LES resolves the turbulent scales.

I'd say 3D is better. 2D suppresses the vortices and/or turbulence fluctuations in the third direction (that you are not considering) thereby resulting in some underpredictions. I'd not say that 2D is not feasible, but I'd stay away from 2D if I'm doing LES. In fact even 2D cases are sometime handled as 3/2D where you have periodicity in the thrid dimension.

matejfor July 16, 2009 08:45

LES is not a robust turbulence model K-eps is robust model. LES resolves turbulence scales and models only the very small ones. If you run 2D LES your results will be rubbish, as the turbulence is not averaged and you must preserve the 3D nature of it. For LES you need much finer grid and small time step and you should know what you're doing. If you want results looking like LES but with cheaper calculation you should try SAS turbulence model (but I do not think it is availible in CCM, you have to go ANSYS to get it).

matej

Maddin July 16, 2009 08:52

In CCM you only have DES when you run unsteady. Steady you don't have this, AFAIK.


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