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-   -   Star-CD and K-Epsilon turbulence model (https://www.cfd-online.com/Forums/star-cd/65016-star-cd-k-epsilon-turbulence-model.html)

 hamoudi June 1, 2009 11:57

Star-CD and K-Epsilon turbulence model

Hello Everybody,

I have a simulation on a numerical jet of air For this I use the Star-CD with Turbulence Model K-epsilon
as you know at the beginning of the simulation we need to initialize the values of
K and epsilon ( Energy and Dissipation rate of turbulence )
to calculate these two parameters
Energy
K = 3 / 2 * (U * I)
Velocity of Jet . U = 286 m / s
I= Intensity = 5 %
K= 360,73 m2/s2

Epsilon

Epsilon = (cmu 3 / 4) * K (3 / 2) / L

cmu = 0,09,

L= M
ixing Length = 0.07

Epsilon = 1,25 e +04

My simulation diverge always

****** Is this possible ********

 matejfor July 16, 2009 08:54

Hi,

in fact you may specify the turbulence at inlet also by turb. intensity and length scale (usualy 0.1 - 0.07 of inlet diameter or characteristic size).

With you high velocity do you calculate the flow as compressible and do you have correct setting of the pressure boundary?

what is diverging, epsilon or continuity (pressure)?

matej

 nowhere July 31, 2009 05:34

Hi,

I am having a somewhat similar problem. For a model i am only given the intensity and length scale for the turbulence model. How (and where) do I specify them in OF?

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