On the boundary condition in the Flow-focusing device demo

Hi,

I am really interested in the results presented in Flow-focusing device demo in the following link.

http://www.palabos.org/features/gallery/26-flow-flocusing-device

I want to do this kind of simulation with finite element method.

I am wondering if somebody can tell me the boundary conditions on the four open ends. If there are some references, it will be better.

Thank you very much.

Best Regards,
Kai