[Shoh]

Hello.
I want to solve the flow and concentration scalar (c) fields around a fan with filter. As can be seen in the attached image, the wind is coming from the west at the speed of 1m/s with c=100. The outlet is the right wall with the boundary conditions of zero-gauge pressure and constant c of 100.

fff2.jpg

Also, there is a rectangular fan which is located at the middle of the bottom wall. At the fan outlet, the velocity is uniform and its magnitude is 1m/s. Thus, the corresponding mass flow will be induced at the fan inlet. Fan also has a filter with the 40% efficiency. But, I want to model the filter as a scalar sink, instead of explicitly modeling it such as a porous medium. That is, scalar at the fan outlet is c=c_in*0.6, where c_in is the scalar at fan inlet. Finally, all walls shown are "infinitesimally thin wall".

My questions are:
1. If we model the fan as an empty space, which boundary conditions should be imposed at the fan inlet and outlet?

2. If we model the fan as a cell zone, which boundary conditions should be imposed at the fan inlet and outlet? In this case, the fan walls, inlet and outlet are infinitesimally thin, i.e face. I first tried like this, but I got a messeage about a zone that has 2 adjacent cell zons.

Please help me please.