How is multiphase cell viscosity defined?
 

In the eulerian-eulerian model, is a the viscosity of any cell given as

Viscosity= VOF(1)*mu(1) + VOF(2)+mu(2) where (1),(2) is phase 1 and 2?

I know this is true of density as shown in theory manual but I have a UDF which is based on this assumption and dont know if it is true.