question: Define_diffusivity
 

The macro 'define_diffusivity' includes 4 arguments. The last is 'i' that identifies the species or UDS. My question is: In my case I used 'species transport' model and two UDS equations. Which does 'i' stand for, the 'i'th specimen or 'i'th UDS? How does FLUENT identify them?

Thank you! braket