Reply To: Pure Ammonia Laminar Flame Speed with FGM Combustion

[abtharpe42]

Over the weekend I figured out what was going on, and it might be a bug in 2023 R1. I'm having the same issue in 2024 R1 on a different device, so the bug might be there too.

If I generate the flamelets in the FGM model, generate the lookup table, and then check the PDF mixture material properties, the "laminar-flame-speed-computed" (LFSC) option was available as shown below:

When I switched to LFSC and then recalculated the properties in the FGM model under the "Properties" tab, the resulting flame speed numbers were corrected for ammonia combustion. However, if I imported a set of pregenerated flamelets into the FGM model OR duplicated a project where a FGM simulation was already completed without LFSC enabled, the LFSC option in the pdf mixture material properties was gone. Also, if a FGM simulation was ran after generating the flamelets and without enabling LFSC before running the calculation, the LFSC option disappears. 

This has been a massive headache, but I figured it out. The major problem with all of this is that the LFSC option disappears entirely beyond the initially setup and I don't know what to do to bring it back. I could find no information about these challenges regarding the FGM laminar flame speed property online or in the User/Theory Guides. I will say that I ended up trying the "laminar-flame-speed-library" (LFSL) option as it was consistently available throughout all of this, and it also fixed the flame speed values for ammonia combustion, but I currently don't know if it's able to handle a mixture of different fuels.

Thanks for the help, I just wish I could reenable the LFSC option after the fact.