[matthias_schreiber]

Dear FOAMers,

I try to get familiar with the twoPhaseEulerFoam-Solver in order to do bubbling fluidized bed simulations in the future. Therefore I started with the tutorial "bed2", but ran into various problems:

a) After some timesteps alpha becomes larger than the setting for alpha_max, finally leading to a blown-up alpha-equation.

Last output:

DILUPBiCG: Solving for alpha, Initial residual = 0.00204016, Final residual = 6.59748e-11, No Iterations 4
Dispersed phase volume fraction = 0.275033 Min(alpha) = -3.08343e-18 Max(alpha) = 0.854645
DILUPBiCG: Solving for alpha, Initial residual = 9.44561e-05, Final residual = 3.20813e-12, No Iterations 4
Dispersed phase volume fraction = 0.275033 Min(alpha) = -3.08222e-18 Max(alpha) = 0.854609
GAMG: Solving for p, Initial residual = 0.00263152, Final residual = 6.91613e-09, No Iterations 27
time step continuity errors : sum local = 2.04471e-09, global = 2.39621e-10, cumulative = 3.95656e-07
DILUPBiCG: Solving for alpha, Initial residual = 0.00101853, Final residual = 5.98548e-11, No Iterations 4
Dispersed phase volume fraction = 0.275033 Min(alpha) = -3.08317e-18 Max(alpha) = 0.854606
DILUPBiCG: Solving for alpha, Initial residual = 8.03968e-05, Final residual = 3.01421e-11, No Iterations 167
Dispersed phase volume fraction = -5.04093 Min(alpha) = -25360.6 Max(alpha) = 8585.28
1 additional process aborted (not shown)

b) The bed expansion is not uniform and looks like a funnel.

Picture:

c) There are "fallen vortices" of high theta values on the side walls of the freeboard.

Picture:

Does anybody has some hints or best-practice guidelines for this kind of simulation with OF?
Many Thanks in advance.

Matthias

[lord_kossity]

Servus Matthias,

there are several threads about twoPhaseEulerFoam.

http://www.cfd-online.com/OpenFOAM_D...es/1/6470.html

http://www.cfd-online.com/OpenFOAM_D...es/1/1019.html

First one is quite general about the parameters in this solver

Second one is more about the issue of convergence problems regarding overpacking.

Regards,
Andreas

[matthias_schreiber]

Hello Andreas,

before posting I searched for related threads and also consulted the ones you mentioned already. Unfortunately I still have problems to set up a converging simulation.

Regards,
Matthias

[lord_kossity]

Hello Matthias,

tomorrow I could send you one of my cases if you are then still intersted in them and provide me your email.

[matthias_schreiber]

Hello Andreas,

this would be very nice. Please use this email address:

matthias.schreiber_at_tu-cottbus.de

Thanks a lot!

Matthias

[matthias_schreiber]

Unfortunately Andreas' case was a bubble column and no fluidzed bed simulation.
So, are there some FOAMers with experience in using kinetic theory for gas-solid fluidzed beds?

Regards,
Matthias