Steady State 2 phase problem
 

Hi everyone,
I am trying to model the flow inside and outside a nozzle in 3D. The flow is created by the pressure difference at the two sides of the nozzle. The water jet produced by the nozzle forms free surface as it comes into contact with the surrounding air before leaving the computational domain. I have modeled the 1/4 of the nozzle, since the case is axis symmetric, created the grid, imported the grid to fluent 6.3.26 and run the case for
Pressure based solver, unsteady, implicit formulation and inviscid fluid. For the two phase model I chose the Explicit VOF model for 2 phases. I have set initial conditions, using patches, for water and air and boundary conditions. I run the simulation and everything runs fine. The results are according to theory.
Then I try to run the same case for steady state, since the problem converges to a steady state solution and in this way I avoid calculating all the intermediate steps. So I choose Pressure based solver, steady, implicit formulation and inviscid fluid. For the two phase model I use the implicit VOF model, as it is suggested here (http://web.njit.edu/topics/Prog_Lang...ml/node541.htm) for steady state problems. I set again the same parameters for boundary and initial conditions. For pressure I use the Body force weighted discretization, as it is suggested here (http://web.njit.edu/topics/Prog_Lang...ml/node541.htm) and all the relaxation factors less than 0.5. When I try to iterate, however, fluent is unable to perform even one iteration. The solver hangs for some time and then I get the message

Error: Floating point error: invalid number
Error Object: ()

Any ideas for that ? What am I doing wrong?
Thanks in advance.