CFD Online Discussion Forums

CFD Online Discussion Forums (http://www.cfd-online.com/Forums/)
-   Main CFD Forum (http://www.cfd-online.com/Forums/main/)
-   -   boundary conditions for K and Epsilon (http://www.cfd-online.com/Forums/main/2957-boundary-conditions-k-epsilon.html)

Hicham January 2, 2001 09:08

boundary conditions for K and Epsilon
 
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)?

Ghanshyam Singh January 2, 2001 11:07

Re: boundary conditions for K and Epsilon
 
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

Abhijit Tilak January 3, 2001 01:22

Re: boundary conditions for K and Epsilon
 
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


All times are GMT -4. The time now is 07:10.