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S1m0n1 March 22, 2013 10:53

Injecting gas
Hi all,

I want to inject different gases into a room similiar to how you inject particles. I want to inject gases like carbon monoxide and see which sections of the room have higher concentrations compared to others.

Can someone help me with injecting a gas?


diamondx March 22, 2013 10:55

you will have to copy paste the material of carbon monoxide in the material list. then activate DPM and selecting what kind of injection you want. How much knowledge you have about this. if none, i suggest you to start by some tutorials about injections...

S1m0n1 March 22, 2013 11:13

Ok, so I guess my question is what size diameter should I set for carbon monoxide? or any gas?

I've injected different particles before, I wasn't sure if injecting particles and gas was the same thing.

Thanks for your reply.

diamondx March 22, 2013 11:21

oh wait, i'm sorry your injecting gas here... my bad...i think droplet are related to liquid fuel. i've never tried to inject gas before :o let me look into it too. sorry about that

S1m0n1 March 22, 2013 11:25

Haha no problem. I tried googling it but I couldn't really find anything on injecting different gases.

oj.bulmer March 22, 2013 11:49

The automised drops of liquid in gas, or solids in liquid/gas hold themselves together as they travel. Thus, they can be represented as point masses and Langrangian equation are solved.

If you inject gases, they will try to diffuse and wander, and in doing so, will lose the initial structure of "gas particle" or whatever we call it.

Are you sure DPM is a right way for it? How about Eulerian models?


S1m0n1 March 22, 2013 11:51

I am not sure if DPM is the right way. I'm relatively new to FLUENT and I've never tried injecting gas. I can look into Eulerian models and see if that is what I am looking for.

Thanks for the suggestion.

Yanlong Li March 23, 2013 06:40

I do not know whether I understood what you want. If you wanna inject two or more different kind of particles, you can use User Variables -> Number of Scalars, it's like UDM for a computional cell, means UDM for every particle.
if you have two kind of particles: a and b. you can set the "Number of Scalars" as "1", when you inject particle a, set the User Variable as "1"; when you inject particle b, set the User Variable as "0" by macro:P_USER_REAL(p,0) = 0. Thus you can tell apart a and b by accessing the variable.

S1m0n1 March 25, 2013 11:30

I am trying to inject a gas at the inlet and see how long it takes to reach the outlet or how long it takes to diffuse. Then I will be able to see the contour of gas concentration and where it is greatest.

asal April 3, 2013 04:46


I have the same question.
I try to inject some water droplets from the surfaces of human body in a room. I need to inject 200 droplet per min and see the concentration in certain part of the room. I try some tutorials, but I cannot succeed. can anyone assist me here?
thanks in advance for your help.

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