Discussion Forum

Hi, I am new to using COMSOL, and I have modelled one species diffusion with the software before. I am trying to model the an ideal scenario of rejuvenator diffusion within a bitumen film layer, and I am a bit confused as to how to go about simulating multi-species diffusion. I selected the Transport of Diluted species in the Physics section and changed the number of species to two, but one of the issues I am having is in the Initial Value tab under Transport of Diluted species section. My confusion is that once on the Initial value tab, there are two concentrations, C1 and C2 that requires an inputs, however, I am not understanding where these concentations correspond to in the geometry, and I am not able to select different portions of the geometry to correspond to these initial concentrations. My second confusion is, in order to simulate this scenario, would I need to add a Fluid Flow type, for example, Laminar Flow. If anyone has any links to tutorials with multi-species diffusion that I can take a look at that may also be helpful. Any resources that could possibly help with tyring to model this scenario would also be very helpful. Thanks.