Hi! all, When we dealing with multi-species flow, in defining the mixture material, it is required to input the mass diffusivity. What does this mass diffusivity refers to? molecular(Di,m) or turbulent(Dt) diffusivity coefficient? if I'm insterested in mixing of two species of water having the same properties, what value should I use for mass diffusivity?

Thanks in Advance!

1. Molecular......

2. If you are interested in the turbulent flow. Turbulent diffusivity is very larger than molecular one, so that some deviation for the mass diffusivity input hardly affects the result. But the effect is fairly large for laminar flow.

SIncerely, Jinwook