multi chemical reaction

[Mohamed]

Hello everyone,

It's possible to run a case with a multi chemical reaction, i have two question please : 

1) how to do it ? 

 

2) how much it's accurate ?

once i tried to run a case and i get this error : the default extinction model is designed for one reaction.

thank you for helping.

Best regards. 

[Kevin]

Does the FDS User's Guide help you?

[Mohamed EL MADRAB]

Hi Kevin,

No !

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EL MADRAB Mohamed

Ingénierie de la Sécurité  Incendie

Aix-Marseille Université

Téléphone : 0665635573

mail : mohamed....@gmail.com

[dr_jfloyd]

Looks like we don't have EXTINCTION_MODEL in the User's Guide or a discussion of what to set it to in the multiple reactions chapter.

[Randy McDermott]

There is no validation for the extinction model for multiple reactions.  Set SUPPRESSION=.FALSE. 

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[dr_jfloyd]

That isn't in the user's guide either. I'll add a note to 12.2.2 so there is some guidance to users.

[Mohamed]

I come back to ask if there was some work done on the V&V of the multiple reactions.

@dr_jfloyd did you add a note to 12.2.2 ?


Thank you  

[Jeremy Q]

Randy's answer for my question concerning two or more fuels. It performs and avoid to set SUPPRESSION = .FALSE.

Try EXTINCTION_MODEL='EXTINCTION 1'.  This invokes the O2-based model (see tech guide appendix).

Unfortunately, this is under development---the current extinction model was not designed for multiple reactions

[Jeremy Q]

Excuse me, my company want to know, if the extinction model for multiple reaction will be implanted in FDS6 or in FDS7 ?

And if it's in FDS7, do you have an idea on when FDS7 will come out ?

thank in advance

[dr_jfloyd]

Multi-reaction extinction is under development, we do not have a targeted release as of yet.  

[Eric MARCHAND]

Hi Dr FLYOD,

I would like, in the following example, to control the start of the combustion, at different times. I have two flammable products, one in a machine, fire starting at T = 0, and I want that the pool of solvent (mixed ethanol type), start only at 120 s, or don't start at t = 0 and I let the FDS solver test whether the pool will start in fire or not.

I tried with a BURNER, to simulate an igniter, but in multi reaction mode, it is not allowed by FDS.

I tried putting a DEVC_ID with appearance at 120 s (INITIAL_STATE = .FALSE.) But the pool appears at T = 0 and ignites immediately.

Which solution do you recommend?

Eric

[dr_jfloyd]

You have defined reactions with infinitely fast chemistry (you did not define E or A).  This means at any temperature the reaction will progress and burn all the fuel and air that mixes together in that time step. If your pool is present at t=0 it will immediately begin to evaporate and that fuel will burn. Add a DEVC_ID to the OBST or VENT defining your ethanol pool and link it to a TIME DEVC with a SETPOINT of 120 s.