[Tobi]

Dear Foamers,

I am working (since 2 weeks) on a very simple simulation.

What I want to simulate:

Something like that: http://www.wiga-energietechnik.de/bi...mage/lwsp2.gif


What I did:

- I meshed the whole geometry with a corse and very fine mesh
- I build polynoms for water thermodynamics (30°C-70°C)
- I changed the thermodynamics for water
- Simulation is LAMINAR

- Inlet 4e-5 m³/s

- At the inlet I have a very simple pipe installation but the solver blow up every time so I just set an Inlet + Outlet (thats all - see pictures).

Now my problem:

Every BC I set make problems.

I am not 100% sure how I should set the p_rgh BC for inlet/outlet/wall.

p is calculated.


For U and T its clear.

The solver is working just for 1 or none iterations.
If I set of the gravity the simulation is working.

It seems that the solver is calculating my water with a compressibility because after the first time step I get extrem huge velocity fields in the big domain.


I tried a lot of BC for U + p_rgh - fixed at the outlet - pressureInletOutletVelocty etc.

Does someone can give me a hint how to set these BC right?

Relaxationfactors are decreased to 0.1.
linearUpwind + limitedLinear schemes are used etc...


Interesting fact:

without gravitation the simulation is working.
With gravitation the mass flux cant be calculated:

--> FOAM FATAL ERROR: 
Continuity error cannot be removed by adjusting the outflow.
Please check the velocity boundary conditions and/or run potentialFoam to initialise the outflow.
Total flux              : 102320
Specified mass inflow   : 0.29563
Specified mass outflow  : 0.151702
Adjustable mass outflow : 0

For gravity I have to set the outlet p_rgh to fixedValue that I can calculate the first timestep but after that the solver blow up again. A picture of p, p_rgh and U is included in the attachment.

The error message:

Time = 2

DILUPBiCG:  Solving for Ux, Initial residual = 0.733571, Final residual = 0.0031127, No Iterations 7
DILUPBiCG:  Solving for Uy, Initial residual = 0.623405, Final residual = 0.000739902, No Iterations 8
DILUPBiCG:  Solving for Uz, Initial residual = 0.701814, Final residual = 0.0023944, No Iterations 7
DILUPBiCG:  Solving for h, Initial residual = 1, Final residual = 0.00132406, No Iterations 2


--> FOAM FATAL ERROR: 
Maximum number of iterations exceeded

    From function thermo<Thermo, Type>::T(scalar f, scalar T0, scalar (thermo<Thermo, Type>::*F)(const scalar) const, scalar (thermo<Thermo, Type>::*dFdT)(const scalar) const, scalar (thermo<Thermo, Type>::*limit)(const scalar) const) const
    in file /home/shorty/OpenFOAM/OpenFOAM-2.2.x/src/thermophysicalModels/specie/lnInclude/thermoI.H at line 76.

FOAM aborting

Compared with the velocity field its clear why its blow up but I can not fix it.


Any suggestions would be appreciated.

Regards Tobi