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Problem with frictional stress model in twoPhaseEulerFoam

Hi everybody,

I run simulations about a bubbling fluidized bed with a central jet trough the solver twoPhaseEulerFoam, with OpenFOAM 2.3.0 .
With the same model proposed in the respective tutorial there are not problem.
When I try to use the fictionalStressModel proposed by Scaeffer, instead of Sinclair and Jackson model, the error below appeares:

Code:

MULES: Solving for alpha.particles

MULES: Solving for alpha.particles

smoothSolver:  Solving for alpha.particles, Initial residual = 0.000210983, Final residual = 9.29629e-10, No Iterations 33

alpha.particles volume fraction = 0.299921  Min(alpha1) = 1.6525e-28  Max(alpha1) = 0.63922

smoothSolver:  Solving for e.particles, Initial residual = 0.181574, Final residual = 5.93711e-07, No Iterations 16

smoothSolver:  Solving for e.air, Initial residual = 0.795681, Final residual = 1.13052e-07, No Iterations 4





--> 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/sergio/rpmbuild/BUILD/OpenFOAM-2.3.0/src/thermophysicalModels/specie/lnInclude/thermoI.H at line 76.



FOAM aborting



#0  Foam::error::printStack(Foam::Ostream&) in "/share/apps/OpenFOAM/OpenFOAM-2.3.0/platforms/linux64GccDPOpt/lib/libOpenFOAM.so"

#1  Foam::error::abort() in "/share/apps/OpenFOAM/OpenFOAM-2.3.0/platforms/linux64GccDPOpt/lib/libOpenFOAM.so"

I try to change relaxation factor, to reduce relative tolerance and increase numbers of outer correctors.
The results is that the source of the error changes: initially it was energy equation, reducing relaxation factor alpha equation became the error, and so on.
Mesh is perfect orthogonal.
Anybody knows why changing the frictional stress model, I get this error?

Thank you.

Hello gianniTre,

I am a little bit confused about your settings. I know the Schaeffer frictional stress model. However I do not know the Sinclair and Jackson frictional stress model, I assume you mean Johnson and Jackson?

Note the warning, maximum number of iterations exceeded. Looks like your pressure solution is not converging... can you try decreasing your time-step, or maybe even increasing your number of corrector loops for the pressure if the decrease in time-step alone does not help?

Kind regards,
Ramon

Hello Ramon,

thank you for your reply, and sorry for the delay in getting back to you.

About Sinclair and Jackson frictional stress model you are right, I mean Johnson and Jackson, I mixed up with the name!

I think that I have resolved my problem:

About correction on pressure loops or decreasing of time step, I tried but the errors did not disappeared.
I obtained convergence only if I use a value of 0.6 for the threshold value of alpha (\alpha_{s,fr,min}) instead of the value usually used in literature (0.63). If there were errors also for this value, for example if I tried different value of inlet velocity or change mesh parameters, I obtained convergence decreasing time step and increasing number of corrector loops for the pressure, but this set up gives a high computational time.

I found strange that I can obtain convergence only for that value of \alpha_{s,fr,min} (in fact if I tried different value errors remains) so I tried to change the solver in the fvSolution for the equation. Originally a smoother solver was used, I use a PCG solver, and I obtained a fast convergence. When some problems arise , I resolved giving a lower value for tolerance of alpha equations or reducing the max Courant number is enough to convergence. The fact that change the solver was enough and I never thinking about it, demonstrates that I am a beginner! :D

In any case thanks for the reply.

Kind regards,
Giovanni