I have a question on what changed between MFIX 23 to 24 in terms of the STIFF chemistry and particle chemistry calculations.
In MFIX 23 I could modify des_reaction_model.f to both change particle size and density as the chemistry was being solved.
In MFIX 24 the same setup does not seem to work. From what I have read the des_reaction_model.f doesnt get called anymore if you are solving STIFF chemistry. Is that correct?
And now there is a new file stiff_chem_dpm.f90 that seems to called when solving STIFF chemistry.
Can someone explain to me what changed and how can I make sure I solve both gas phase and solid phase reactions and have the particle size and density be updated like I had in MFIX 23?
Stiff solver support for DEM was added with the 23.3 release. If you modify the source code for a given release, it is not recommended to carry the modified code to other releases, as it is likely to not be compatible. You can take a look at Energy Analysis | netl.doe.gov for more details of the dem stiff solver implementation (found on the MFiX documentation page).
I would also highly recommend switching to the latest version (25.3 as of the time of writing).
I’ve been using 23.2 where I could use usr_rates and usr_rates_des for the chemistry and des_reaction_model.f to change the particle size and density according to the reaction chemistry. In both 24.4.1 and 25.3 I am not able to do that anymore.. I modified the appropriate des_reaction_model.f with similar modifications as done in 23.2, which is not difficult, but I can’t seem to get the size and density to change at the same time like before. I don’t understand what changed in the way the calculations are carried out that usr_rates + des_reaction_model doesnt work anymore.
I’ve had a lot of issues with 25.3 on the meshing side. So thats why I am using 24.4.1 which was a vetted version internally.
I have a very simple geometry of a conical fluidized bed and for some reason in 25.3 it always crashes when its trying to write the MESH VTU file.. The same issue does not happen for 24.4.1 or 23.2.. One of my colleagues mentioned he had seen some discussions about problems in the 25 mesher, but I have not found such discussions.
Sure, I can do that. But I still don’t understand why I am not able to make size and density of the particles change using reaction rates like I was doing before. Going to 25.3 wont make a difference because they seem to have the same modification, whatever it was, that is causing this difference.
I’ve been using 23.2 where I could use usr_rates and usr_rates_des for the chemistry and des_reaction_model.f to change the particle size and density according to the reaction chemistry. In both 24.4.1 and 25.3 I am not able to do that anymore.. I modified the appropriate des_reaction_model.f with similar modifications as done in 23.2, which is not difficult, but I can’t seem to get the size and density to change at the same time like before. I don’t understand what changed in the way the calculations are carried out that usr_rates + des_reaction_model doesnt work anymore.
Can you explain or refer me to documentation that explains the change?
I’m concerned about the reported meshing issues in 25.3, especially since we are preparing the 26.1 release. @jiujitsu11 can you please upload a bug report so we can check this out?