No erro message, nor diverge, but simulation stopped in a sudden!

MFiX How to
#1

Hi, I am doing a DEM 2D simulation with reactions with mfix-19.3.0 GUI(windows)
Here is my case set-up
biomass_pyrolysis_2020-01-08T154540.679513.zip (157.6 KB)

I encoutered a problem: the simulation stops at 0.037s without any erro message, nor diverge. The residual seems normal.

residual
residual1168×628 11.5 KB

The last output message is :

11 1.1E-03 8.9E-05 1.2E-04 P0
12 6.8E-04 5.3E-05 7.3E-05 P0
DT= 0.3138E-03 NIT/s=43905
Integrating stiff chemistry…
DONE.
Minimum/Maximum number of steps over all cells: 3/3
Number of cells with Homogeneous/Heterogeneous reactions: 0/1725
Maximum number of integration attempts: 1
CPU Time Used: 0.0312 sec
Timestep walltime, fluid solver: 0.391 s
DEM NITs: 1863 Total PIP: 3418
Previous MFiX run is resumable. Reset job to edit model
MFiX process has stopped
(mfix-19.3.0) E:\Works\MFix_results\fbtry\biomass_pyrolysis_2020_1_7>endlocal

I didn’t set any batch queue end. It seems the simulation ends in a sudden without any sign.

#2

I catch my mistake!
I guess it stops at 0.03s because only from 0.03s it began to inject biomass particle and having reactions.
So I added this line in the des_usr_rates.f

write(,) ‘DES_rates(Pyrolysis)=’, DES_rates(Pyrolysis)

and I got

DES_rates(Pyrolysis)= 21585669385.050713
Integrating stiff chemistry…

exactly at t=0.03s
Then the simulation suddenly stopped.

So the problem happens when calculating the Pyrolysis, it is too big.

#3

Hi, Please let me know how you solved this issue. I am also facing same kind of problem.

#4

Hello, friend. I am very glad to help you but I have already forgotten what I did. If you don’t mind I can send you a copy of my current case, though I am not sure whether it is the same problem with this post.

#5

Thank you so much for your prompt reply. Would love to study your case. Please share your case file.

#6

biomass_pyrolysis_2020-01-16T094043.456740.zip (1.8 MB)
sorry for late

Now I guess the parallel simulation may be the cause
When I use SMP, 4 cores, on ubantu , it will stop suddenly at 0.115s with no message
but when it run on Windows with serial simulation, it goes well.

#7

Note that mfix version 20.1 and newer are better about printing error messages from numeric calculations. We weren’t properly catching all zero-division and overflow errors so some of these resulted in silent program termination without any error messages. The newer versions will print a stack trace when any floatint point exceptions occur.

#8

thank you for advising, I am now updated to 20.1 version

#9

Hello,

I’m currently working on 21.1.4 version and this is still happening (the solver terminates without showing an error). Can you please check my topic and help?

Here is the link to the topic:

Thanks,
Mariam