Using more than one reaction in the same simulation

[Jesper Scott Johnsen]

Hi there

 

I hope someone know if it is possible to use two different reactions in the same simulation, and if it is possible how to do this.

 

The issue is that I want to start with one fire with a certain soot yield and later I want another fire with another soot yield to takeover. Is that possible in one way or another?

 

Thanks in advance!

 

BR

Jesper

[Kevin]

You can set SOOT_YIELD=0. on the REAC line, and then create a gas
species

&SPEC ID='my soot', MW=?? /

that can serve as a surrogate. Then you use MASS_FLUX on the SURF line
to control the generation rate of your surrogate smoke.

On Oct 18, 4:53 am, Jesper Scott Johnsen

[Craig Weinschenk]

Jesper,

To answer you first question, in the latest code the answer is yes. If you have the repository checked out, see the example in /Verification/Energy_Budget/energy_budget_adiabatic_two_fuels.fds In this example there are two separate reactions take place - polyurethane and wood. Both reactions are sourced from the same vent using MASS_FLUX on the SURF line, but they could easily be sourced from two separate vents if you so chose. Also, use can use the RAMP function on MASS_FLUX to stagger the start of the reactions as well.

For your second question, you defined reactions with two different SOOT_YIELD on two REAC lines, then RAMP the first reaction down and RAMP the second reaction up when you want the different soot yield.

-Craig

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Craig Weinschenk

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Fire Engineering Division

National Institute of Standards and Technology
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[Sam]

Hi Craig,

I have the same query as the author, Is there any way to do this for a simple reaction? Without having to balance the chemical reaction, input mass flux etc

Kind regards,

Sam

[dr_jfloyd]

The simple chemistry inputs are only for a single fuel with a single set of post-flame yields. If you wish to do anything more complex you will need to explicitly define the reaction and the species participating in the reaction. 

While it may seem like this is simple from a user point of view, from a software development view dealing with the current simple chemistry inputs while still allowing for arbitrarily complex chemistry requires a significant amount of complex logic woven throughout the input file processing (maintaining FDS would actually be a lot easier if we required everyone to fully specify all SPEC and REAC). Adding a lot more complexity to the simple chemistry inputs would not be a small development effort.