Turbulent kinetic energy in k-epsilon model
Hello,
I am a newbie here and I got a trouble when calculating turbulent kinetic energy in standard k-epsilon model which I hope anyone out there please help me :) My problem is like this: I picked 1 point in my cubit domain, run Fluent and exported turbulent kinetic energy at (for example) time step 100, that was fine But I have to do the manual calculation, then I used the equation: turbulent kinetic energy: k=1.5*(u_avg*I)^2 turbulence intensity: I=u'/u_avg where: u_avg, u' are mean flow velocity and velocity fluctuation I did study the theory and user guides but I still don't know how to calculate u_avg and u', spatial average or time average? then I did 3 cases: - u_avg = u of that point which I exported from Fluent after running - u_avg = spatial average velocity (mean velocity of total cubic domain at time step 100) - u_avg = time average velocity (mean velocity of that single point over 100 time steps) actually, I used these values to multiply with turbulence intensity I that i export from Fluent to get k (as equation above) because I am not sure how to calculate u', but unfortunately they were all wrong (compare to the value of k I exported) I know that maybe this is a stupid question but I really confused, so can you guys plz explain for me? It would be very appreciated. Thank you in advance. Regards, Thao Nguyen |
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