Simulation and revelation of smoke of a smoldering fire Edit
By default, FDS assumes that the smoke from a fire is generated in direct proportion to the heat release rate. A value of SOOT_YIELD=0.01 on the REAC line means that the smoke generation rate is 1% of the fuel burning rate. The smoke in this case is not explicitly tracked by FDS, but rather is assumed to be a function of the mixture fraction variables that are explicitly tracked.
Suppose, however, that you want to define your own smoke and that you want to specify its production rate independently of the HRR (or even instead of an actual fire, like a smoldering source). You also want to define a mass extinction coefficient for the smoke and an assumed molecular weight (as it will be tracked like a gas specie). Finally, you also want to visualize the smoke using the SMOKE3D feature in Smokeview.
Use the following lines:
&SPEC ID='my smoke', MW=29., MASS_EXTINCTION_COEFFICIENT=8700. / &SURF ID='smolder', TMP_FRONT=1000., MASS_FLUX(1)=0.0001, COLOR='RED' / &VENT XB=0.6,1.0,0.3,0.7,0.0,0.0, SURF_ID='smolder' / &PROP ID='Acme Smoke', QUANTITY='CHAMBER OBSCURATION', SPEC_ID='my smoke' / &DEVC XYZ=1.00,0.50,0.95, PROP_ID='Acme Smoke', ID='smoke_1' / &DUMP SMOKE3D_QUANTITY='my smoke', DT_PL3D=30. /