boundary conditions for K and Epsilon

January 2, 2001, 09:08

I make modeling of the air flows in the greenhouses with the model K-epsilon and I ask you which values for the boundary conditions I must put in inlet for the turbulent kinetic energie (k) and for the dissipation of this energie (epsilon)?

January 2, 2001, 11:07

What is the Reynolds number in your case? Just to begin with, you can assume turbulent intensity around 5% at the inlet. Calculate K and epsilon based on this and compare the results with the experimental data. You may get reasonable match.

GS

January 3, 2001, 01:22

hi,

To start with as mentioned by Ghanshyam u need to know typical values of turbulent intensity in flows u are solving. then assume some value of eddy viscosity say Mu_eff=20*Mu_laminar (to be correct molecular viscosity) then calculate k as

k_inlet= (U_in*TU)**2 Tu=turbulent intensity.

U_in=sqrt(u*u+v*v+w*w) e_inlet= (Cmu*rho_inlet*(k_inlet)**2)/Mu_eff

hope this helps

abhijit

January 2, 2001, 09:08	boundary conditions for K and Epsilon	#1
Hicham Guest Posts: n/a	I make modeling of the air flows in the greenhouses with the model K-epsilon and I ask you which values for the boundary conditions I must put in inlet for the turbulent kinetic energie (k) and for the dissipation of this energie (epsilon)?

January 2, 2001, 11:07	Re: boundary conditions for K and Epsilon	#2
Ghanshyam Singh Guest Posts: n/a	What is the Reynolds number in your case? Just to begin with, you can assume turbulent intensity around 5% at the inlet. Calculate K and epsilon based on this and compare the results with the experimental data. You may get reasonable match. GS

January 3, 2001, 01:22	Re: boundary conditions for K and Epsilon	#3
Abhijit Tilak Guest Posts: n/a	hi, To start with as mentioned by Ghanshyam u need to know typical values of turbulent intensity in flows u are solving. then assume some value of eddy viscosity say Mu_eff=20Mu_laminar (to be correct molecular viscosity) then calculate k as k_inlet= (U_inTU)*2 Tu=turbulent intensity. U_in=sqrt(uu+vv+ww) e_inlet= (Cmurho_inlet(k_inlet)**2)/Mu_eff hope this helps abhijit

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