period BC in streamwise.

Jonas Holdeman

I don't think you can use periodic boundary conditions for your problem as stated. As you note, there will be a pressure drop along the section and periodic b.c. would result in multivalued pressure and density.

I can imagine using periodic b.c. if you had a nonconservative body force like an electromagnetic pump driving the flow, in which case the pressure gradient could be zero and so the inlet and outlet pressures would match.

You would not specify initial or inlet flow as the solution should evolve to fully-developed Poiseulle flow over time.