Pipe flow behaving unexpectedly
 

Hi,
I am running a simple pressure driven pipe flow simulations. There is a pressure inlet boundary condition to the inlet of the pipe. The pipe diameter increases abruptly creating a step. The pipe then bifurcates. At the end of the pipe there are two nozzles, i.e. N1 and N2. These nozzles open into two separate pipes (secondary pipes) which have pressure outlet boundary conditions. N1 and N2 have different pressures. Pressure of N1, PN1 > PN2. There is a recirculation region seen at the initial step near the inlet. It is situated towards the N1 which seems ok as PN1 > PN2. But next when we modifiy the secondary pipes keepin everything same. The recirculation bubble is shifted towards N2 from N1. But the pressure still reads as PN1>PN2 (although PN1 is almost same, PN2 has increased, but still PN1>PN2). This is baffling. Could you throw some light on this issue. The mesh is identical in both the cases. The case set-up is also identical.