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Calculation of initial k for RAS turbulence models

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Old   August 28, 2013, 01:45
Default Calculation of initial k for RAS turbulence models
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Baris (Heewa)
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Dear Foam users,

I want to ask about the initial calculation of k (turbulence kinetic energy). I am studying cavitating flow inside of the nozzle with different turbulence models ( kepsilon, RNGkepsilon, kwSST).

According to users guide k is calculated with this formula: k=3/2(u)^2

u corresponds to fluctuating velocity which equals to 5% of inlet velocity. Just i am confused about this point. As you can see in the attached figure i have one domain inlet (Vin=3.1 m/s) and one nozzle inlet (Vin=12.8m/s). AS you know that cavitation and turbulence take place close the nozzle inlet.

I tried both inlet velocity for calculation initial value of k and final result of calculation not change too much, but i want to know that which inlet velocity value should be used for initial calculation of k for the nozzle flows.

thanks in advance.
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Old   August 28, 2013, 03:52
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i think you better set the values of main entrance for velocity and length(for omega or epsilon formulas)
Because only at boundaries you should use a model,the rest of geometry should be solved by the solver itself.
Correct me if anyone has another opinion.
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