I need help; 'oxygen mass fraction' or 'carbone monoxide mass fraction ' output quantity

[fds-quang]

Hi, I'm new to FDS6. I want to know how to output the mass fraction of species with the mixture fraction model. In FDS5, we use quantity='oxygen  mass fraction' or quantity='carbone monoxide mass fraction'. How to do it in FDS6. Thanks in advance.

[dr_jfloyd]

Have you tried reading the User's Guide?

[Craig Weinschenk]

Please see the User Guide section on species and Mass Fraction output quantity.

On Jan 20, 2014 11:50 AM, "fds-quang" <cunco...@gmail.com> wrote:

Hi, I'm new to FDS6. I want to know how to output the mass fraction of species with the mixture fraction model. In FDS5, we use quantity='oxygen  mass fraction' or quantity='carbone monoxide mass fraction'. How to do it in FDS6. Thanks in advance.

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[fds-quang]

Yes, i've tried to read the user guide but an find only the information for the predefined species: SPEC_ID='OXYGEN', QUANTITY='MASS FRACTION'. But with the mixture fraction model, we don't define any species, and we use the lowercase letters for all the species like: oxygen, carbone monoxide ..... Is it right with FDS6? I just want to know how to output the mass fraction and why we don't use 'oxygen mass fraction' in FDS6.     

[dr_jfloyd]

There is no mixture fraction model in FDS 6. Review the theory manual for details.

In terms of species:

User's Guide 12.1.1

When simple chemistry is being used, FDS will automatically create three lumped species: AIR, FUEL, and PRODUCTS. The actual name of the fuel species will be the name given on the REAC line (for example
MY FUEL in the last sample above). FDS creates these lumped species in the same manner as you would in an input file. FDS first defines the primitive species and then defines the lumped species. In essence FDS internally creates input lines like those shown in Example 2 of Section 11.2. This means when doing simple chemistry, that even though you did not explicitly define oxygen in the input file, you can request an output for oxygen since it was implicitly defined by FDS.

Table 11.1 gives you the names of the primitive species. OXYGEN, CARBON DIOXIDE, etc.

So if you are using simple chemistry and want the oxygen mass fraction:
QUANTITY='MASS FRACTION', SPEC_ID='OXYGEN'/

[mikael...@gmail.com]

I've read the user guide and most of the Techncical Reference Guides for FDS 6, and I hadn't noticed that you had removed the "mixture fraction" model. When considering a simple chemistry one step combustion reaction (which from what I gather is what most people still do), how is FDS 6 different from previous version such that it can no longer be called a mixture fraction model? I'd appreciate a small elaboration or a more specific reference, but I understand that the dev team can't tutor everyone. Thanks.