CFD Online Discussion Forums

CFD Online Discussion Forums (http://www.cfd-online.com/Forums/)
-   OpenFOAM (http://www.cfd-online.com/Forums/openfoam/)
-   -   divU-terms in k-eps equations (http://www.cfd-online.com/Forums/openfoam/63230-divu-terms-k-eps-equations.html)

mabinty April 1, 2009 10:43

divU-terms in k-eps equations
 
Dear all!

Could somebody tell me please, where the terms

>> fvm::SuSp(((2.0/3.0)*C1_ + C3_)*rho_*divU, epsilon_)

and

>> fvm::SuSp((2.0/3.0)*rho_*divU, k_)

in the dissipation- and k-equation of the compressible RAS model come from (kEpsilon.C)? I searched the forum for further explanation but was not successful. Thanks in advance!!

Aram

natrask June 18, 2009 11:41

They come from the double inner product of the velocity gradient with the Reynolds stress tensor in the production terms

i.e, for the epsilon equation, there should be a production term

C1*R_{ij}&&grad(U)

in the kEpsilon.C implemented in foam,
R_{ij} = (2.0/3.0)*I)*k_ - (mut_/rho_)*dev(twoSymm(fvc::grad(U_))

is split into two parts for stability reasons

the first term
C1_*G*epsilon_/k_
contains the contribution from the second term in the R_{ij} equation

the second term
- fvm::SuSp(((2.0/3.0)*C1_ + C3_)*rho_*divU, epsilon_)
contains the contribution from the (2/3)I*k term

Best,
Nat

mabinty June 19, 2009 04:17

Nat,

thanks a lot for the clarification!!

Best regards,
Aram


All times are GMT -4. The time now is 09:54.