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initial concentration in multicomponent mixtures

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Old   April 26, 2004, 07:40
Default initial concentration in multicomponent mixtures
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Hi, I have two flow channels, each one has an inlet and an outlet boundaries and they are totally separated from one another, also each one has a different ternary mixture. When trying to set the concentration of the different componentes i.e. scalars at the inlet boundaries a strange thing happen. The program takes the concentration at the boundary of only the first scalar in the scalar list. You can see it in the boundary in the 'define boundary regions' folder in the GUI. You set the concentration of the first scalar in the list in the 'scalar boundary' folder, and automatically the default concentration at one inlet boundary is that value and the other inlet boundary has a default concentration of 0. This is a problem, because in a case when there are two inlets and the first scalar on the list is only part of one of the two mixtures, then the other channel will have a wrong concetration value. To clarify, let me give you an example. The first scalar on my list is N2, followed by O2 and H2O. N2 has a concentration (mass fraction) of 0.7, O2 0.2 and H2O 0.1. I run the model and my subroutines use the concentration of these scalars to calculates some other passive scalars. Then when I plot the values of these passive scalars, for instance the molar fraction of H2O, which should be something like 0.09, starts with a default calues of 0.7 and the goes gradually down to 0.09. This is totally wrong!!! Any way, thanks for reading, any suggestions will be very helpfull, many thanks. Isidro
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