[CoolKau]

I also have the common issue with the Maximum Numbers or iterations exceeded.

The error is posted below and my boundary conditions are attached.

I followed some other posts on this forum. I see that I have some issues with my k: "bounding k, min: -3.02372e-16" which should not be negative. I also have some time step continuity errors. CheckMesh suggests my mesh is good.

I tried to resolve this issue by changing my boundary conditions until I replaced all in- and outlets by "inletOutlet" conditions but the problem persists. Is there anything obvious that I am missing? Any of my solvers ill defined?

Time = 2.862e-06

Courant Number mean: 1.71229e-06 max: 4.77408e-05
diagonal:  Solving for rho, Initial residual = 0, Final residual = 0, No Iterations 0
DILUPBiCG:  Solving for Ux, Initial residual = 1.21865e-06, Final residual = 1.21865e-06, No Iterations 0
DILUPBiCG:  Solving for Uy, Initial residual = 3.70323e-07, Final residual = 3.70323e-07, No Iterations 0
DILUPBiCG:  Solving for Uz, Initial residual = 5.21823e-07, Final residual = 5.21823e-07, No Iterations 0
DILUPBiCG:  Solving for e, Initial residual = 8.44715e-06, Final residual = 8.44715e-06, No Iterations 0
DILUPBiCG:  Solving for p, Initial residual = 2.14661e-07, Final residual = 8.68781e-14, No Iterations 1
diagonal:  Solving for rho, Initial residual = 0, Final residual = 0, No Iterations 0
time step continuity errors : sum local = 4.76017e-13, global = 2.82656e-13, cumulative = -4.55667e-07
DILUPBiCG:  Solving for p, Initial residual = 4.23269e-08, Final residual = 1.07341e-13, No Iterations 1
diagonal:  Solving for rho, Initial residual = 0, Final residual = 0, No Iterations 0
time step continuity errors : sum local = 5.97663e-13, global = -1.82462e-13, cumulative = -4.55667e-07
DILUPBiCG:  Solving for omega, Initial residual = 5.9302e-09, Final residual = 5.9302e-09, No Iterations 0
DILUPBiCG:  Solving for k, Initial residual = 1.45588e-07, Final residual = 8.98881e-09, No Iterations 7
bounding k, min: -3.02372e-16 max: 1 average: 0.0025831
ExecutionTime = 2131.95 s  ClockTime = 2149 s

Time = 2.864e-06

Courant Number mean: 1.38724e-05 max: 59.186
diagonal:  Solving for rho, Initial residual = 0, Final residual = 0, No Iterations 0
DILUPBiCG:  Solving for Ux, Initial residual = 1.21516e-06, Final residual = 1.21516e-06, No Iterations 0
DILUPBiCG:  Solving for Uy, Initial residual = 3.70533e-07, Final residual = 3.70533e-07, No Iterations 0
DILUPBiCG:  Solving for Uz, Initial residual = 5.21286e-07, Final residual = 5.21286e-07, No Iterations 0
DILUPBiCG:  Solving for e, Initial residual = 8.44715e-06, Final residual = 8.44715e-06, No Iterations 0

[19] --> FOAM FATAL ERROR: 
[19] Maximum number of iterations exceeded
[19] 
[19]     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
[19]     in file /apps/OpenFOAM//OpenFOAM-2.2.1/src/thermophysicalModels/specie/lnInclude/thermoI.H at line 76.
[19] 
FOAM parallel run aborting

[alexeym]

Hi,

the line

Courant Number mean: 1.38724e-05 max: 59.186

suggests that you've got diverging solution. So if you try to describe the problem you're trying to solve in more details, maybe someone will come up with a solution. Right now it's not clear what solver you're using, why you've decided to use certain BCs, and why do you think problem should converge.

[CoolKau]

Thank you for your reply alexeym.

I indeed forgot the mention the solver. It is sonicFoam.

The geometry of the setup very simple: it is a capillary which is transversely filled with gas via inlets. At both ends the capillary connects to outflow boxes which are essentially at vacuum. The inlets should be at a constant pressure, the boundaries surrounding the outlet at a very low pressure.

Regards the boundary conditions, I am no expert. So I chose those boundary conditions which seemed to be reasonable from reading through this forum and the tutorials. However, I replaced all of them such that I was left with "inletOutlet" (or "outletInlets") and walls. And the simulation still did not converge. The main idea is to have a defined high pressure on the inlet and a low pressure at the outlet. Temperature at the inlet and walls is also known. The remaining values are free.

I run several simulations with different pressure at the inlets some of them run until the end and some of them run into a "max iteration" with and without the Courant number exploding. However, I can get most of the simulations to run until the end when I play with the timestep or the number of processors after the simulation crashed. The results are as expected and I cant find any surprising values at the time steps where the simulation crashed. I used OpenFoam 2.2. With OpenFoam 2.3 the stability has gotten significantly worse.