Dear Dr. Amine,nnYes it is my thesis subject to investigate the influence of the multiphase model I am using the Eulerian-Eulerian approach!nThe first mu_mix is the viscosity of the mixture according to the carreau-yasuda model. However, since you cannot enter a mixture viscosity in the two-phase model, I compute the viscosity of the rbc's in order to implement it in fluent.nDo you mean you do not require an UDF for rbc density since it is not taken into account in the model? I wanted to include it for completeness and since the previous researcher also did so.nnThanks!nnMichellen