Error: Species definition not provided

[M.J]

Hello, I am a student learning FDS on my own. I am trying to model a situation where PMMA decomposes to release MMA gas, leading to a combustion reaction. Therefore, I have defined the MMA formula and specific heat, viscosity coefficient, and diffusivity coefficient for REAC_FUEL using RAMP. However, I am receiving the following warning message: 'SPEC REAC_FUEL is not in the table of pre-defined species. Any unassigned SPEC variables in the input were assigned the properties of nitrogen.' I thought I had defined it additionally, but I'm not sure what additional input values I need to add or modify. I would appreciate any advice. Thank you.

&SPEC ID='WATER VAPOR'/
&SPEC ID='OXYGEN'/
&SPEC ID='CARBON DIOXIDE'/
&RAMP ID='REAC_FUEL_RAMP_MU', T=98.85, F=9.44E-6/
&RAMP ID='REAC_FUEL_RAMP_MU', T=100.855, F=0.015/
&RAMP ID='REAC_FUEL_RAMP_MU', T=126.85, F=0.01692/
&RAMP ID='REAC_FUEL_RAMP_MU', T=326.85, F=0.0319/
&RAMP ID='REAC_FUEL_RAMP_MU', T=526.85, F=0.04836/
&RAMP ID='REAC_FUEL_RAMP_MU', T=626.85, F=0.057145/
&RAMP ID='REAC_FUEL_RAMP_MU', T=727.85, F=2.45E-5/
&RAMP ID='REAC_FUEL_RAMP_D', T=0.0, F=7.64E-6/
&RAMP ID='REAC_FUEL_RAMP_D', T=13.85, F=7.64E-6/
&RAMP ID='REAC_FUEL_RAMP_D', T=15.85, F=7.69E-6/
&RAMP ID='REAC_FUEL_RAMP_D', T=126.85, F=1.35E-5/
&RAMP ID='REAC_FUEL_RAMP_D', T=326.85, F=2.76E-5/
&RAMP ID='REAC_FUEL_RAMP_D', T=526.85, F=4.57E-5/
&RAMP ID='REAC_FUEL_RAMP_D', T=626.85, F=5.61E-5/
&RAMP ID='REAC_FUEL_RAMP_D', T=727.85, F=1.37E-4/
&RAMP ID='REAC_FUEL_RAMP_CP', T=13.85, F=0.753/
&RAMP ID='REAC_FUEL_RAMP_CP', T=15.85, F=0.7571/
&RAMP ID='REAC_FUEL_RAMP_CP', T=126.85, F=1.0569/
&RAMP ID='REAC_FUEL_RAMP_CP', T=326.85, F=1.5105/
&RAMP ID='REAC_FUEL_RAMP_CP', T=526.85, F=1.8541/
&RAMP ID='REAC_FUEL_RAMP_CP', T=626.85, F=1.9852/
&RAMP ID='REAC_FUEL_RAMP_CP', T=727.85, F=2.09/
&SPEC ID='REAC_FUEL', FORMULA='C5H8O2', RAMP_D='REAC_FUEL_RAMP_D', RAMP_MU='REAC_FUEL_RAMP_MU', RAMP_CP='REAC_FUEL_RAMP_CP'/

&REAC ID='SFPE PMMA',
      FYI='SFPE Handbook, 5th Edition, Tables A.38 and A.39',
      HEAT_OF_COMBUSTION=2.42E+4,
      FUEL='REAC_FUEL',
      SPEC_ID_NU='OXYGEN','REAC_FUEL','WATER VAPOR','CARBON DIOXIDE',
      NU=-6.0,-1.0,4.0,5.0/

&MATL ID='PMMA',
      SPECIFIC_HEAT=1.69,
      CONDUCTIVITY=0.336,
      DENSITY=1155.0,
      ABSORPTION_COEFFICIENT=2240.0,
      N_REACTIONS=1,
      HEAT_OF_REACTION=1830.0,
      A=8.6E+12,
      E=1.881E+5,
      SPEC_ID=REAC_FUEL,
      NU_SPEC=1/

[Ed Wynn]

That warning message is harmless -- you can ignore it. (In fact, I think I worked through the relevant part of the source code once, and found that the message is inevitable if you use a fuel other than the predefined ones. Perhaps I should have reported it as a bug, but it didn't seem like a high priority.)

I haven't checked your setup in any detail (and I am not affiliated with FDS at all, so please ignore me if you get more expert advice). The values in REAC_FUEL_RAMP_MU look very high for viscosity of a vapour.

[dr_jfloyd]

The warning is not a bug. It is letting you know that you are not using a predefined species for the fuel. At that point it is encumbent on you at the point to satisfy yourself that the assumptions that FDS makes for thermophysical properties are reasonable for your specific usage of FDS.

[Randy McDermott]

To Ed's point, if it were me, I would do a very simple test case with PENTANE (C5) as my fuel to compare the viscosity values and make sure you don't have a units error.

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