Solution settings for soot model (method of moments)
I have set up a reacting flow 2D-model (asymmetric-swirl) that includes of GRI-3 mechanism, turbulence, radiation and soot.
I tried to solve it step by step, from cold flow to addition of the modules one by one. Now in the complete model, after around 500k iterations, the divergence on soot model is occurring. I tried to reduce the URF for soot model, but it is not helping and divergence happens soon or late!
The message I get is as below:
Stabilizing soot-mom-2-moment to enhance linear solver robustness.
Stabilizing soot-mom-2-moment using GMRES to enhance linear solver robustness.
Divergence detected in AMG solver: soot-mom-2-moment
I also tried to set the solver settings for soot, from flexible to V-cyle with BGSTAB, but it did not help.
My first question: is 'soot-mom-2-moment' about 'soot moment 2' itself? or is it about interaction between soot and momentum?
the plot of residuals at this step is as follows, where the soot-mom-0 shows fluctuation, but the divergence message is about soot-mom-2:
Here are the URFs I've set:
pressure, density: 0.3
body forces, turbulence factors, momentum: 0.7
energy, P1: 0.9
soot: 0.6 (I tried 0.5, 0.4, they also diverge after some more iterations)
What do you think about the origin of this divergence? and how you think I can make the solution stable?
Many thanks in advance for your ideas,