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density of a multi component mixture

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Old   April 23, 2012, 16:24
Default density of a multi component mixture
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Aditya
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Hi,

I have a mixture of 55% xenon, 35% hydrogen and 15%oxygen by mass fraction in a bubble surrounded by nitrogen medium.

By calculating the density using ideal gas the denisty of bubble should be greater than the density of nitrogen but the bubble turns out to be less denser than the surrounding nitrogen medium.

I have a UDF for specifying mass fractions and when I have only Xe and oxygen the bubble is denser than nitrogen but the moment hydrogen is added (even as little as 0.01 mass fraction), the bubble goes way below the density of surrounding nitrogen.

SETUP: DRIVEN SECTION OF TEH SHOC TUBE WITH NITROGEN AS THE SHOCK TUBE AND A BUBBLE AT THE CENTER.

someone please help.
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Old   April 24, 2012, 01:25
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Mohammad Ghazvini
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Maybe that problem will resolve if you increase the number of grids.
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Old   April 24, 2012, 02:12
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Aditya
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do you think resolving the mesh would help the calculation of density?

im just curious. I will try everything to fix this problem.

but can you just outline ur thought process.
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Old   April 24, 2012, 19:19
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Mohammad Ghazvini
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Yes it will sometimes.
in gas mixtures averaging causes problems, so the larger is the grid size, the larger is the averaging effect.
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Old   April 24, 2012, 21:50
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sounds good. I will try the mesh refinement and will let yoou know immeditaely.

Thanks a lot once again for the advice.
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Old   April 25, 2012, 12:31
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hey,

I have tried refining the mesh but it didnt work. Can you suggest me some other idea for the problem.?
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