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Old   November 21, 2012, 18:04
Default species transport convergence
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Ali Emadi
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Hi friends
I'm simulating a laminar diffusion CH4/Air flame using laminar species transport. I use Arrhenius approach for simple CH4+2 O2---> CO2 + 2 H2Oreaction, in order to calculate species production and consumption rates.
I used the key guides advised by fluent user guide as follow:

1- simulation of fuel and air without reaction(cold flow)
2- enabling volumetric reaction and stiff chemistry
3- setting density relaxation factor between 0.5 and 1.
4- patching a high temperature zone to ignite fuel and air mixture

I did the above procedure but there exist no stable flame and convergence. at the beginning of second simulation(with reaction) flame ignite in small zone, which has high temperature, but does not propagate into domain. in fact it go out of the domain by flow. I attached domain, mixing and ignited flame at two iterates.

can anyone say what is wrong or what is missed?
Attached Images
File Type: jpg flame-2piece2-200mm.jpg (70.2 KB, 28 views)
File Type: jpg CH4 mass fraction.jpg (53.0 KB, 29 views)
File Type: jpg patched Temperature.jpg (50.3 KB, 20 views)
File Type: jpg rate of reaction1.jpg (50.9 KB, 22 views)
File Type: jpg rate of reaction2.jpg (52.2 KB, 21 views)
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Old   November 14, 2016, 10:30
Default Enable option: Stiff chemistry solver
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luong hung truyen
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For the problem of laminar flame. When defining the model, in the section of transport species. there is an option of Stiff chemistry solver. You should enable this option.


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convergence problem, diffusion flame, species transport

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