I'm currently simulating gas species reactions inside a chemical vapour deposition chamber. Some of the reactions I have modelled diverges. All the material properties I defined are based on ideal gas law and kinetic theory. The rate laws are not Arrhenius relation, so I have defined UDF for the reaction rates. The problem I have is that, whenever I run the simulation, the console shows me warning message about mass diffusivity being zero, and for several seconds, the simulation crashes with a divergence error. I have tried everything including decrease the reaction rate law by 1000000 times, only then the simulation converges, but that's not right. I would hope that someone know to solve or at least has seen this problem before could help me figure out what's wrong!

hi..chen

i faced the similar problem" divergence in AMG solver: species 2" when i am running methane-air combustion problem. since i didn't write any udf i simply changed relaxation parameter from 1 to 0.8 or 0.7 for that corresponding species 2.. it worked... i think your problem is much more complex than this .. try once like this..good luck.