density of a multi component mixture

dsn2491 · April 23, 2012, 17:24

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.

mahmohammad · April 24, 2012, 02:25

Maybe that problem will resolve if you increase the number of grids.

dsn2491 · April 24, 2012, 03:12

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.

mahmohammad · April 24, 2012, 20:19

Yes it will sometimes.
in gas mixtures averaging causes problems, so the larger is the grid size, the larger is the averaging effect.

dsn2491 · April 24, 2012, 22:50

sounds good. I will try the mesh refinement and will let yoou know immeditaely.

Thanks a lot once again for the advice.

dsn2491 · April 25, 2012, 13:31

hey,

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

April 23, 2012, 17:24	density of a multi component mixture	#1
dsn2491 New Member Aditya Join Date: Dec 2011 Posts: 28 Rep Power: 15	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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April 24, 2012, 02:25		#2
mahmohammad New Member Mohammad Ghazvini Join Date: Mar 2010 Posts: 16 Rep Power: 16	Maybe that problem will resolve if you increase the number of grids.

April 24, 2012, 03:12		#3
dsn2491 New Member Aditya Join Date: Dec 2011 Posts: 28 Rep Power: 15	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.

April 24, 2012, 20:19		#4
mahmohammad New Member Mohammad Ghazvini Join Date: Mar 2010 Posts: 16 Rep Power: 16	Yes it will sometimes. in gas mixtures averaging causes problems, so the larger is the grid size, the larger is the averaging effect.

April 24, 2012, 22:50		#5
dsn2491 New Member Aditya Join Date: Dec 2011 Posts: 28 Rep Power: 15	sounds good. I will try the mesh refinement and will let yoou know immeditaely. Thanks a lot once again for the advice.

April 25, 2012, 13:31		#6
dsn2491 New Member Aditya Join Date: Dec 2011 Posts: 28 Rep Power: 15	hey, I have tried refining the mesh but it didnt work. Can you suggest me some other idea for the problem.?