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2 inlets, 2 outlets, % of outlet fluid which comes from each inlet

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Old   July 19, 2017, 12:33
Default 2 inlets, 2 outlets, % of outlet fluid which comes from each inlet
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Hello !

I'm sorry if this question has already been asked on this forum, I searched it but didn't find my answer.

I have one question :
I have a 3D system with 2 inlets and 2 outlets. I would like to know if it's possible for FLUENT to know or mesure, for an outlet, the % of fluid which comes from each inlet.
(for exemple: for the first outlet, 67% comes from Inlet1 et 33% comes from Inlet2)

Thanks
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Old   July 21, 2017, 05:58
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Hello,
You can very well use the post processing of ANSYS to find the mass flow rates. Go to Results tab and you can integrate the velocity profile at the outlet with the area to get the mass flow rate.
m dot = integral (rho .dv A)
Then after finding the respective mass flow rates find your ratio or your desired quantity.
I hope I answered your question

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Old   July 21, 2017, 09:21
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Hello Abhinand, Thanks so much for your help.

I think I understood : I need to integrate the velocity profile of the outlet 1 or 2 with the area of the inlet 1 or 2 and i will know the mass flow rate of the outlet i chose which comes from the inlet i chose, is that correct ?

I tried this expression in the "Expression Tab" in the post processing of ANSYS:

areaInt(Density*(Velocity u*Normal X + Velocity v*Normal Y + Velocity w*Normal Z))@outlet_2

The problem is that I don't know how to specifie to FLUENT that "Velocity u" is the velocity of the inlet 1 or 2. Do you know how to do that ? Thank you in advance
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Old   July 21, 2017, 09:47
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I think you misunderstood quite a lot of things
You cannot integrate the velocity profile of outlet 1 and integrate with area of inlet.
The mass flow rate at outlet 1 would be a contribution of both inlet 1 and inlet 2

Im taking a guess here,
You would have to find out the velocity to the outlet by switching off either of the inlets and interpolate to find out which vectors of inlet 1 reaches outlet 1 and outlet2
Could you explain a bit more like with a CAD file or better problem statement.

One other way is to use Particle track. You can enable all your inlets and outlet and track the number of particles that reach your location from a desired amount given from inlet. That will give you a rough ratio of the mass flow rate. I think this would be a better way to proceed. Hope I have answered


Cheers

Last edited by Abhinand; July 21, 2017 at 09:57. Reason: Another solution
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Old   July 21, 2017, 11:03
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Sorry to misundertsood what you said, i just discovered CFD this month,
Thank you again

I attached a drawing of my system (a little bit simplified). I would like to know the quantity of fluid of inlet 2 which "arrives" in outlet 2.

I think that if i switch off inlet 1 as you said, the resultat will change, no ?

Ok, thank you, Particle Track seems to be a good way to do it. I think I will use it if i can't do it with the post processing of ANSYS
Attached Images
File Type: jpg 2inlets_2outlets.jpg (76.9 KB, 7 views)
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Old   July 21, 2017, 11:35
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Particle tracking is the best way to find the ratio, I believe.
Good luck
Cheers
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Old   July 21, 2017, 16:46
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Use a scalar transport equation or the passive scalar approach. Seed each inlet with your passive scalar, then you'll know exactly how much mass came from where based on the value of the passive scalar. I.e. put a passive scalar of 1 for one inlet and 0 for the other. The value of the passive scalar at every location tells you what you are looking for.

I don't recommend the particle tracking approach, it's not equivalent and far less elegant.
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Old   July 24, 2017, 04:48
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Hello LuckyTran
Thank you so much for your help

I tried to use your method with "Scalar transport equation". This is what I did :
Define/ User defined/ Scalars
Number of User-Defined Scalars = 1
Solution Zone for index 0 = all fluid zone
Flux Function = none

Material panel
UDS Diffusivity = defined-per-uds

Boundary conditions/ inlet1/ UDS/ User defined scalar boundary value = 1
Boundary conditions/ inlet2/ UDS/ User defined scalar boundary value = 0

I'm sorry but I don't really understand what i need to display after completed my calculation. Is it the value of the scalar in one of the 2 outlets ?

Thanks

Last edited by Jabb; July 24, 2017 at 10:45.
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