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Old   November 6, 2002, 18:41
Default Species and reactions
  #1
Ale
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Hi,

if you select hydrogen-air as the mixture material, you will see that this mixture includes 9 volumetric species (H2, O2, H2O, O, H, OH, H2O2, HO2, N2), but only 1 global volumetric reaction (H2 + 1/2 O2 ---> H2O).

How can it predict so many species with such a simple kinetics? How does Fluent calculate the source terms for all these species?

Can anybody answer to these questions?

Thanks a lot.
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Old   November 9, 2002, 21:31
Default Re: Species and reactions
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Jin-Wook LEE
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You can not predict the so many species with such a simple kinetics. Use PDF approach by using prePDF. prePDF is based on the 'fast chemistry'. I think that H2+O2 reaction can be regarded as 'fast chemistry'. Then you can predict many species, upto 20 for current Fluent version.

Sincerely, Jinwook

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Old   November 11, 2002, 17:28
Default Re: Species and reactions
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Ale
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Thank you Jinwook for your answer. I know that with such a simple kinetics I cannot predict so many species, that's what makes me surprised.

If you enable Species Transport in Fluent 6, you can choose the hydrogen-air mixture, and see that in the mixture there are the 9 species I mentioned.

If you enable Volumetric reaction, and you look in the materials panel, you will see that there is only one reaction (that is the global reaction of hydrogen oxidation).

What I would like to know is: how can fluent calculate the concentrations of all the species in the mixture, if it apparently takes into account only one reaction, involving just H2, O2, and H2O?

I hope that now my question is more clear...

Regards,

Ale
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