Define Profile, using mass fraction of different point
 

Hi,

I try to simulate a large flow field with a fan which sucks in a mixture at point 1 and blows it out at point 2 of the flow field. I know how to make the faces for inlet and outlet and how to define the velocities, but I am a bit lost on how to define the mass fractions correctly.

I want to define the inlet (point 2 - inlet from point of view of the flow field, it is the outlet of the fan) as having the same mass fraction as in the outlet (outlet from point of view of the flow field, inlet of the fan at point 1).

I imagine a UDF for for the inlet (point 2) which "copies" the mass fraction of the outlet (point 1), but I have no idea how to define it.

I know the C_YI macro to get the mass fraction, but this has the thread as parameter which is basically just the thread of faces of the current inlet face, right? Is there anything like C_YI (x,y,z) ?

Kind Regards