Multiple Species
Since the gas molecules do not interact with each other in the flow domain, solving for many different species at once does not significantly increase the computational complexity of the problem. It is possible to model flows involving several different species simultaneously by adding more species in the Dependent Variables section.
For an example of using multiple species in a model, see the example Ultrahigh Vacuum, Chemical Vapor Deposition (Application Library path: Molecular_Flow_Module/Industrial_Applications/uhv_cvd).
Modeling multiple species is needed if adsorption and desorption of the molecules occurs. It is also possible for the different species to interact on the surfaces — for example, if they share common adsorption sites, the site occupancy can be set up as an expression involving the concentration of both gas molecules.