Soot modelling in FDS

[Sagar Singhal]

Hi,

Does any of the versions of FDS consider soot modeling? I am interested in looking at the soot volume fraction field from pool fire. I read a thesis titled  CFD SIMULATION OF SOOT FORMATION AND FLAME RADIATION by Christopher William Lautenberger where the author talks about soot model based on mixture fraction and temperature.

Thanks,

Sagar

[Randy McDermott]

FDS does not use a mixture fraction-based combustion model.  It uses the eddy dissipation model.  How much soot is produced depends on how you set the number of reactions and the stoichiometry.  Search the user guide for SOOT_YIELD, which determines the post-flame soot yield.  To control in-flame soot, you need to set the N_SIMPLE_CHEMISTRY_REACTIONS=2 on REAC.  Then you can control the in-flame soot using FUEL_C_TO_CO_RATIO.  These parameters are discussed in the user guide.

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[Sagar Singhal]

Thanks for the reply, but in this case, the flame soot field will highly depend on the choice of FUEL_C_TO_CO_RATIO. How to get the correct value of this fraction for different fuels to predict the correct radiative fraction? Does any of the previous versions which use a mixture fraction-based combustion have the capability of modeling soot as discussed in the above cited paper?

[dr_jfloyd]

Chris's work was done on his own branch of FDS and was never incorporated into the release version of the source. 

Good question on how to know what the correct the value. This is an area of active investigation; however, predicting the correct radiative fraction involves more than just the in-flame soot value - path length, accounting for subgrid effects, etc. all impact the prediction of radiant fraction and are also areas of active investigaton (see the FDS Road Map at https://github.com/firemodels/fds/wiki/FDS-Road-Map).