Two inlets! One air and one mix of gases

Dary · November 20, 2012, 11:53

Hi, Iam new here. want to see if anyone can help me with a fluent case. I want to see how the gases mixes. So I have two inlets that goes into one "basket" with different velocity and temperature for the inlets: One inlet with air and one inlet with 0.122 of H2, 0.21 of CO2, 32.2 of H2O and 34 of N2.
I need help with how to set-up this in Fluent.

RodriguezFatz · November 21, 2012, 07:30

At first you need to decide which multiphase model you want to use. There you can also set the number of phases to 5. Than just add the materials (gases) you need under "Material" and assign the gases to the five different phases under "Phases".

Dary · November 21, 2012, 09:37

Thanx, I have tryed that, BUT using the phase I cant have all the gases in one phase.
I am running simulation with species and let see how it goes.

RodriguezFatz · November 21, 2012, 09:40

No, you can not have all gases in one phase!?!? That's the clue - having different phases... I think I don't understand what you try to say, this does not make sense at all to me.

Dary · November 21, 2012, 10:17

Sry but as I said iam new with this. What I did now is i created phases for each gas and when setting BC I choose air for one onlet and for the other inlet i choose the created phases with their volume fractions. Thats how you mean it should be ??
again thanx for ur time.

RodriguezFatz · November 21, 2012, 10:32

Yep. But which multiphase model do you use?
(This wasn't ment rude. I really thought we are talking at cross purposes...)

Dary · November 21, 2012, 10:55

Just got me, this is not a multiphase problem. Not that advanced. I just need to simulate the behavier of the air and these components how they mixes. I think I should use species for this? Or any other suggestions?

RodriguezFatz · November 21, 2012, 13:19

What do you mean by "how they mix"? If put different gases into one box and want to know how exactly they mix, that is a multiphase problem...

Anyone else who gets the point?

ghost82 · November 22, 2012, 02:41

Hi Dary,
in my opinion you have to use the species model; since gases mix at a molecular level, species approach is ok.
More in general, when fluids mix at a molecular level the problem is multi-species; when the mix is macroscopic, then the problem is multiphase.

Daniele

Dary · November 23, 2012, 10:32

Hi, thank you both for the help. i used species and i found out that that is a good approuch. I have another question: i have load = 0.0392mol/sec how to I put that as velocity inlet??? thank you guys

Johnyi · November 28, 2012, 23:44

Sure you need to use multispecies model. You need to convert the mol to volume, for example
24.79 dm3/mol at 25 °C.and calculate the velocity according to your inlet area.

After you define the inlet velocity, you need to specify different percentage for each specie

vancuong.nguyen · February 17, 2013, 22:40

Hi Dary,
I am new CFD user and getting the problems with setting up BC. Could you please let me know how to choose air for one of the inlet? I already got the fraction choice.
btw, if possible for us to simulate with the inlet flow rate change along with time?

Thanks a lot!

November 20, 2012, 11:53	Two inlets! One air and one mix of gases	#1
Dary New Member dary Join Date: Nov 2012 Posts: 5 Rep Power: 13	Hi, Iam new here. want to see if anyone can help me with a fluent case. I want to see how the gases mixes. So I have two inlets that goes into one "basket" with different velocity and temperature for the inlets: One inlet with air and one inlet with 0.122 of H2, 0.21 of CO2, 32.2 of H2O and 34 of N2. I need help with how to set-up this in Fluent.

November 21, 2012, 07:30		#2
RodriguezFatz Senior Member Philipp Join Date: Jun 2011 Location: Germany Posts: 1,297 Rep Power: 26	At first you need to decide which multiphase model you want to use. There you can also set the number of phases to 5. Than just add the materials (gases) you need under "Material" and assign the gases to the five different phases under "Phases".

November 21, 2012, 09:37		#3
Dary New Member dary Join Date: Nov 2012 Posts: 5 Rep Power: 13	Thanx, I have tryed that, BUT using the phase I cant have all the gases in one phase. I am running simulation with species and let see how it goes.

November 21, 2012, 09:40		#4
RodriguezFatz Senior Member Philipp Join Date: Jun 2011 Location: Germany Posts: 1,297 Rep Power: 26	No, you can not have all gases in one phase!?!? That's the clue - having different phases... I think I don't understand what you try to say, this does not make sense at all to me.

November 21, 2012, 10:17		#5
Dary New Member dary Join Date: Nov 2012 Posts: 5 Rep Power: 13	Sry but as I said iam new with this. What I did now is i created phases for each gas and when setting BC I choose air for one onlet and for the other inlet i choose the created phases with their volume fractions. Thats how you mean it should be ?? again thanx for ur time.

November 21, 2012, 10:32		#6
RodriguezFatz Senior Member Philipp Join Date: Jun 2011 Location: Germany Posts: 1,297 Rep Power: 26	Yep. But which multiphase model do you use? (This wasn't ment rude. I really thought we are talking at cross purposes...)

November 21, 2012, 10:55		#7
Dary New Member dary Join Date: Nov 2012 Posts: 5 Rep Power: 13	Just got me, this is not a multiphase problem. Not that advanced. I just need to simulate the behavier of the air and these components how they mixes. I think I should use species for this? Or any other suggestions?

November 21, 2012, 13:19		#8
RodriguezFatz Senior Member Philipp Join Date: Jun 2011 Location: Germany Posts: 1,297 Rep Power: 26	What do you mean by "how they mix"? If put different gases into one box and want to know how exactly they mix, that is a multiphase problem... Anyone else who gets the point?

November 22, 2012, 02:41		#9
ghost82 Senior Member Rick Join Date: Oct 2010 Posts: 1,016 Rep Power: 26	Hi Dary, in my opinion you have to use the species model; since gases mix at a molecular level, species approach is ok. More in general, when fluids mix at a molecular level the problem is multi-species; when the mix is macroscopic, then the problem is multiphase. Daniele

November 23, 2012, 10:32		#10
Dary New Member dary Join Date: Nov 2012 Posts: 5 Rep Power: 13	Hi, thank you both for the help. i used species and i found out that that is a good approuch. I have another question: i have load = 0.0392mol/sec how to I put that as velocity inlet??? thank you guys

November 28, 2012, 23:44		#11
Johnyi New Member Johnny Join Date: Aug 2012 Posts: 3 Rep Power: 13	Sure you need to use multispecies model. You need to convert the mol to volume, for example 24.79 dm3/mol at 25 °C.and calculate the velocity according to your inlet area. After you define the inlet velocity, you need to specify different percentage for each specie

February 17, 2013, 22:40		#12
vancuong.nguyen New Member Cuong Join Date: Feb 2013 Posts: 1 Rep Power: 0	Hi Dary, I am new CFD user and getting the problems with setting up BC. Could you please let me know how to choose air for one of the inlet? I already got the fraction choice. btw, if possible for us to simulate with the inlet flow rate change along with time? Thanks a lot!