Multispecies sections can be used for fluid flow analyses to describe the different materials and behaviors for each species in the simulation. When you add materials to a multispecies section, the first material you specify is considered the "background" material for the section to which you add additional materials. The additional materials you add to the background material must include diffusivity data in their material definitions. You can use multispecies sections in the same model as fluid sections or porous sections to simulate the flow of species across a fluid-fluid interface from the multispecies section into the other section types. However, when you combine these section types, you must specify the background species of the multispecies section as the material flowing through the porous or fluid sections. | ||||||