Non-reactive gaseous mixing

sbkashif · July 27, 2015, 06:04

Hello CFDOnline community,

Greetings!!

I intend to study the mixing of two gases in a non-reactive environment and I intend to seek opinion on the appropriate model to use along with the technique to quantify the extent of mixing based on the results.

Firstly, as per my literature review, I guess species model is more appropriate but I would like to hear about the other relevant models that could be used.

Secondly, using the given model and the boundary conditions, what results could we expect and how would we quantify the extent of mixing using these results.

Lastly, can the related(or near related) tutorial/technique could be provided for CFX platform?

Thank you in advance

ghorrocks · July 27, 2015, 06:35

I do not understand most of your question, but if the two gases have the same physical properties then you can use an additional variable to do this. If they have different material properties then you need to use a multicomponent mixture.

If you use a multicomponent mixture then you can see the mixing by looking at the mass fractions.

sbkashif · July 27, 2015, 07:00

I am using gases of different physical properties.

Considering the use of multimixture model and ultimately having volume/mass fraction contours, my concern is that how can I quantitatively measure the extent of mixing of two gases.

ghorrocks · July 27, 2015, 07:08

It is up to you how to measure it, there are many different ways. How about the thickness from the 10% mf.a point to the 10%mf.b point? Or the volume between 10% and 90% mf? If you look in the literature I am sure you will find lots of definitions of mixing.

sbkashif · July 27, 2015, 10:00

Thank you sir for your time in addressing my queries. I have a few more which could possibly lead to the final answer.

1.Please clarify that the method you suggested (multicomponent mixture) is valid for non-reactive mixing as well (particularly the change in volume fraction)? If yes, how could I interpret such results in CFX post.

2.To elaborate more on my problem, I am looking for some mixing index or a dimensionless number etc which could represent the extent of gas mixing. I would be grateful if you could guide me to any specific literature (gas-gas mixing) in this regard which you would have come across, if comfortable at your end.

ghorrocks · July 27, 2015, 18:16

Yes, multicomponent mixture is valid for non-reacting mixtures. Note you will be modelling mass fractions, not volume fractions.

This is not my area of expertise so do not have references I can point you to. But a literature search should find information on this.

July 27, 2015, 06:04	Non-reactive gaseous mixing	#1
sbkashif New Member Join Date: Jul 2015 Posts: 10 Rep Power: 10	Hello CFDOnline community, Greetings!! I intend to study the mixing of two gases in a non-reactive environment and I intend to seek opinion on the appropriate model to use along with the technique to quantify the extent of mixing based on the results. Firstly, as per my literature review, I guess species model is more appropriate but I would like to hear about the other relevant models that could be used. Secondly, using the given model and the boundary conditions, what results could we expect and how would we quantify the extent of mixing using these results. Lastly, can the related(or near related) tutorial/technique could be provided for CFX platform? Thank you in advance

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July 27, 2015, 06:35		#2
ghorrocks Super Moderator Glenn Horrocks Join Date: Mar 2009 Location: Sydney, Australia Posts: 17,697 Rep Power: 143	I do not understand most of your question, but if the two gases have the same physical properties then you can use an additional variable to do this. If they have different material properties then you need to use a multicomponent mixture. If you use a multicomponent mixture then you can see the mixing by looking at the mass fractions.

July 27, 2015, 07:00		#3
sbkashif New Member Join Date: Jul 2015 Posts: 10 Rep Power: 10	I am using gases of different physical properties. Considering the use of multimixture model and ultimately having volume/mass fraction contours, my concern is that how can I quantitatively measure the extent of mixing of two gases.

July 27, 2015, 07:08		#4
ghorrocks Super Moderator Glenn Horrocks Join Date: Mar 2009 Location: Sydney, Australia Posts: 17,697 Rep Power: 143	It is up to you how to measure it, there are many different ways. How about the thickness from the 10% mf.a point to the 10%mf.b point? Or the volume between 10% and 90% mf? If you look in the literature I am sure you will find lots of definitions of mixing.

July 27, 2015, 10:00		#5
sbkashif New Member Join Date: Jul 2015 Posts: 10 Rep Power: 10	Thank you sir for your time in addressing my queries. I have a few more which could possibly lead to the final answer. 1.Please clarify that the method you suggested (multicomponent mixture) is valid for non-reactive mixing as well (particularly the change in volume fraction)? If yes, how could I interpret such results in CFX post. 2.To elaborate more on my problem, I am looking for some mixing index or a dimensionless number etc which could represent the extent of gas mixing. I would be grateful if you could guide me to any specific literature (gas-gas mixing) in this regard which you would have come across, if comfortable at your end.

July 27, 2015, 18:16		#6
ghorrocks Super Moderator Glenn Horrocks Join Date: Mar 2009 Location: Sydney, Australia Posts: 17,697 Rep Power: 143	Yes, multicomponent mixture is valid for non-reacting mixtures. Note you will be modelling mass fractions, not volume fractions. This is not my area of expertise so do not have references I can point you to. But a literature search should find information on this.