Viscosity computation in interFoam with VOF method
 

Hi everyone,

It would be appreciated if someone could help me to explain the method for viscosity computation in interFoam.
From theory of VOF method, density and dynamics viscosity of mixture flow near interface are computed as:
rho = alpha*rho1 + (1-alpha)*rho2
mu = alpha*mu1 + (1-alpha)*mu2

However, when I check source "incompressibleTwoPhaseMixture.H" and "incompressibleTwoPhaseMixture.C", I found the following code:

"mu",
limitedAlpha1*rho1_*nuModel1_->nu()
+ (scalar(1) - limitedAlpha1)*rho2_*nuModel2_->nu()
and:
nu_ = mu()/(limitedAlpha1*rho1_ + (scalar(1) - limitedAlpha1)*rho2_);


as I understand, the source code are corresponding to the following fomular:
mu = alpha*rho1*nu1 + (1-alpha)*rho2*nu2;
and nu = mu/(alpha1*rho1+ (1-alpha)*rho2);

Therefore, I think this is not true with the theory of VOF method.
Could you please someone help me to correct my understanding??

Thanks