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defining mixture of gases in a domain

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Old   May 31, 2018, 10:35
Default defining mixture of gases in a domain
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Muhammad Ali Uzair
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Dear all,

i am simulating a species transport problem.
For that, I have to define mixture of gases by volume percentage (CO2+H2O+O2+N2=100%) in a rectangular domain.

How can I do that? Thanks
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Old   May 31, 2018, 11:08
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Do you have a species transport problem or do you simply want to model it as a mixture of gases? It doesn't mean the same thing.

Specifying the gas mixture in the domain is done in cell zone conditions. In a species transport problem, you don't know the composition beforehand, you have to solve for it with the calculate button. Here you only give an initial guess.
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Old   May 31, 2018, 11:17
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Quote:
Originally Posted by LuckyTran View Post
Do you have a species transport problem or do you simply want to model it as a mixture of gases? It doesn't mean the same thing.

Specifying the gas mixture in the domain is done in cell zone conditions. In a species transport problem, you don't know the composition beforehand, you have to solve for it with the calculate button. Here you only give an initial guess.
Thanks dear,

how can I do it in cell zone conditions, i.e. defining mixture by volume percentage?

tbh my problem is like this; there is an inlet of air, and then there is a mixture of gases with known percentages of volume inside the domain. and I have to do the species transport.
and I cannot use the species transport, then what is the way to to that?
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Old   June 1, 2018, 20:11
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Ok so you need to use the species transport model. Specify the composition of air at the inlet as a boundary condition. For the interior with a predefined mixture, you would specify the mass fractions as the initial condition in the initialization. Normally you would specify mass fractions because that's the primitive variable in the species transport, but sometimes you are allowed to specify mole fractions.
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