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Dary November 20, 2012 12:53

Two inlets! One air and one mix of gases
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 08:30

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 10:37

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 10:40

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 11:17

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 11:32

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 11:55

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 14:19

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 03:41

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.


Dary November 23, 2012 11:32

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 29, 2012 00:44

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 23:40

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!

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