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-   -   k and epsilon (http://www.cfd-online.com/Forums/numeca/77542-k-epsilon.html)

safikhani_hamed June 26, 2010 04:36

k and epsilon
 
Dear all,
I want to model a centrifugal pump in NUMECA using k-eps turbulence model, how ever I just have intensity and length scale at inlet, how can I convert intensity and length scale to k and epsilon at inlet ?

sincerely

Hamidzoka June 30, 2010 07:06

Dear Hamed;
if pump inlet velocity is known, ( inlet velocity may be calculated by knowing pump flow rate and pump suction side diameter) you can find k from turbulence intensity relation.
calculated k can be applied to length scale relation to find epsilon.

does it help?

sanboju January 24, 2011 09:44

Hi Amed,

Sorry because the late answer.

As you know, k is the kinetic energy and epsilon is the disipation of turbulence. We could consider epsilon as 0.1*k. The kinetic energy k, can be calculated as: k=3/2 (T*U)^2, where T is the Temperature of the problem, and U is the inlet velocity.

I hope I'll be helpful.

Cheers

sanboju January 26, 2011 12:10

Tu
 
Hi,

Sorry because of the definition of the other day. As you know in a turbulence model, the units for k are [m^2/s^2]. I was wrong saying T was the temperature of the model, T is is a percentatge that represents the turbulence intensity factor as I've seen on biography. I realise because of my job results, intensity of the turbulence and the poor disipation.

T = 0.05-0.10 (biography, fluctuations respecte wind velocity)
U= inlet velocity

Sorry if someone have run their jobs after my definition of k but I wouldn't get results yet.

k= 3/2(T*U)^2
epsilon = 0.1*k

Greatings,
sanboju


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