[rks171]

I wrote a two-phase, 1-D CFD code. It has a segregated solver and a full coupled solver. I just can't seem to get the residuals to behave. They keep oscillating all over the place. Furthermore, my pressure profile looks completely unrealistic for most of the cases I test. I'm trying to model some experimental tests of two-phase flow in a pipe that discharges into a vessel full of water. The boundary conditions I give to my code are:

1) mass flow rate at the pipe inlet
2) pressure at the pipe outlet
3) volume fraction of the vapor at the inlet (the experiment gives the flow quality at the inlet)
4) volume fraction of the vapor at the outlet (since the pipe discharges to a large vessel filled with water, I set this value to zero)

I'm wondering if I'm allowed to specify the volume fraction on both ends of the pipe like I have. It looks like the void profile tries to take a shape but then suddenly jumps down at the end to satisfy the boundary condition. Could this be the cause of the unrealistic pressure profile and the ill-behaved residuals?