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Old   July 8, 2013, 07:56
Unhappy LES Combustion Boundary Condition
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hi all,

I am currently developing an LES model for combustion using the flamelet/non-premixed combustion model but I am having a problem...

I calculate the correct air and fuel inlet boundary conditions (I have tried both velocity inlet and mass-flow inlet), and I know they are correct as when I run them with the k-epsilon model it gives the correct overall mixture fraction and peak flame temperature, etc.

But then when I run it with LES for a while (1-2 flow throughs) the fuel concentration becomes too low and the time-averaged mixture fraction becomes lower than that initially calculated or predicted by the RANS run.

I then need to increase the fuel flow until the model gives the correct overall average mixture fraction or equivalence ratio (at the outlet).

Has anyone else encountered this issue?

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Old   July 11, 2013, 07:23
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can anyone share any insight? even the smallest clue could help a lot...
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combustion, les

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