It does not make a sense to enter a mixture viscosity for Eulerian Multiphase. Here better to enter the same viscosity for both phases which will do the trick. Or you enter for mu_rbc the expression required so that the mixture viscosity is the same as you wrote for your formula something like nmur_rbc=mu_plasma(Function-(1-alpha_rbc))/(alpha_rbc)nnImagine you want to enter the expression for RBC via DEFINE_PROPERTY you do not need to access any other threads: everything is provided to you right away. Be aware here that variables like strain rate are phase specific. The return value will be used laminar viscosity.nnIn Eulerian the momentum equations are solved for each phase: so mixture properties are not used for solving!