[jason]

Hi, I would like to use OF for estimating the pressure losses in a piping arrangement. The problem consists of an inlet and an outlet and some pipes, bends, reductions and enlargements inbetween. The inlet has a known flowrate and the outlet has a known pressure. I would like to estimate what the inlet pressure would be so that a suitable pump can be chosen for the system.

I appreciate this is a straightforward problem and that I can to some extent calculate this by hand. I have tried to do this in OF using a decent mesh of a 300mm dia pipe, a fixed velocity inlet (eg 3m/s) and a pressure outlet (eg 2.5bar) and no-slip walls. I have two problems:

1/ Using simpleFoam set to laminar or turbulent, everything converges fine. The velocity predictions are as expected however the pressure losses are miniscule (eg 0.001 bar) which I cannot believe. I have a nice believable velocity profile in the pipe sections and separation where expected.

2/ If I set the initial (0) internal field to anything other than the same as the outlet pressure (2.5bar) the solution diverges. I've tried the nonorthogonal correction but it doesn't help.

Not wanting to blow my own trumpet but I have worked in CFD for 15 years so hopefully I havent made too many mistakes in the problem setup. I would also be confident of obtaining a decent solution using this mesh in say Star or Fluent.

Hope you can enlighten.

Jason