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Star-CD and K-Epsilon turbulence model

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Old   June 1, 2009, 11:57
Smile Star-CD and K-Epsilon turbulence model
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Hamoudi djamel
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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


Please I am waiting for your Answers



****** Is this possible ********
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Old   July 16, 2009, 08:54
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matej forman
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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
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Old   July 31, 2009, 05:34
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nick stoppelkamp
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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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