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Counting Particles in Transient Simulation

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Old   August 14, 2017, 04:37
Question Counting Particles in Transient Simulation
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Hello there,

Im currently working on a Transient Particle Simulation for my bachelor thesis.

1.) Is there any way to count the Particles on Boundries over the time ?

For example:

How many particles pass the Inlet in those ten seconds of Simulation?

2.) if 1. is possible, can I get a distribution on where those particles pass a Boundry or an interface?

Im using Ansys R18.0 via Ansys Workbench.

Thanks for your help


Edit:

I searched the Ansys Modelling guide but couldnt find anything that helps.
Tried the Particle Histograms in Output Control but that gives a Histogram for each Timestep.
Expressions like count(Water.Mean Particle Number)@Inlet or sum(Water.Mean Particle Number)@Inlet didnt work either.

(Sorry if these are very basic questions but Im quite new to simulating and could find answers through Google or the Modeling/Theory Guide)

Last edited by Nuuu; August 14, 2017 at 11:41. Reason: Further Details
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Old   August 15, 2017, 03:20
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Anyone ?
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Old   August 15, 2017, 06:19
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Have you tried integrating "Particle Number Rate" over the boundary?

I don't do much particle tracking stuff, so sorry I can't help you more.
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Old   August 15, 2017, 07:17
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Are you speaking of massFlowInt(Water.Particle Number Rate)@Inlet? since I cant specify Int(Water.Particle Number Rate) to a specific boundary.

With massFlowInt(...)@... I got the following error:
No data exists for varible 'Water.Particle Number Rate' specifierd in object 'Inlet'.

Does that mean I did monitored my particles correctly ?
My particles are seeded in the Inlet and I tried to evaluate this expression in CFD-Post.

No worries. Im glad somebody answered.
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Old   August 15, 2017, 07:59
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Yes, I meant integrate in general. I left it up to you to work out exactly what form of integration and how to implement it

I would suggest you do areaInt(Particle Phase.Particle Number Rate)@Boundary.

Area integral seems more appropriate than mass flow integral, but check what basis the particle number rate is based on (volume flow rate or mass flow rate) to be sure.

Also, you need to do this operation on your particle phase, not the continuous phase. Is water your continuous phase? If so that would explain why that did not work.
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Old   August 15, 2017, 09:10
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Water is my particle Phase and air my continuous phase.

with areaInt I get the exact same error message:

No data exists for varible 'Water.Particle Number Rate' specifierd in object 'Inlet'.

The Number Rate is base on a direct Specification. I set 1 [s^-1] at the Inlet.
Even if I have this Value I still must be able to get the Value at the Outlet somehow.
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Old   August 15, 2017, 18:34
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There will be some way of getting it, but it is just a matter of finding exactly what. As I am no expert on particle tracking I cannot help you there.

But an alternate approach is to get the mass flow rate of your particle phase. If your size distribution is known you can work out the particle count from that.
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Old   April 14, 2020, 10:41
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At the end did you understand how you can count the particles that pass a certain surface? I would also be interested in the same thing .. but is it necessary in CFX Pre to set additional variables as a variable? Because in my .res I don't find Water.Particle Number Rate




Quote:
Originally Posted by Nuuu View Post
Water is my particle Phase and air my continuous phase.

with areaInt I get the exact same error message:

No data exists for varible 'Water.Particle Number Rate' specifierd in object 'Inlet'.

The Number Rate is base on a direct Specification. I set 1 [s^-1] at the Inlet.
Even if I have this Value I still must be able to get the Value at the Outlet somehow.
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Old   October 8, 2020, 17:11
Default Particle mass flow rate
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Hello all,
I am simulating a particle track of contaminant particles in a cleanroom using ANSYS CFX particle transport model. Along with this i also have to check the concentration of contaminants in the room. The particles are generated by machines and flow with the velocity of air flow in the room.As i am tracking the motion of particles from a point on the machine, i have put the particle mass flow rate as zero. But, i am not able to get particle volume fraction when i put particle mass flow rate as zero.

1. Can anyone please tell me how to solve this problem?
2. What does the particle mass flow rate imply in ANSYS?. Is it the rate of generation particle in the machine?

Thank you,
Ganesh
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Old   October 8, 2020, 17:19
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Are you using a Eularian or Lagrangian particle tracking model? A Eularian model sounds best based on what I guess you are trying to do.
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Old   October 8, 2020, 17:32
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Hello ghorrocks,
I am using lagrangian model since the particle volume fraction is very low. The size of particles i am tracking range from 0.5 micron to 5 micron.

Thank you,
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Old   October 8, 2020, 17:53
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Low particle count does not imply the Lagrangian model is better. The Eularian model handles low particle count just fine as well.

The reason I suggest the Eularian model is because working out particle flow rates much easier than the Lagrangian model, and it is easier to set up and run as well. I only use Lagrangian models when the exact path taken by every particle is important.
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Old   October 8, 2020, 18:05
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Hello Glen,
Thank you for your suggestions. I shall go through the eulerian model.
Is it easy to switch to the eulerian model, with the details available while using lagrangian model.?

Thank you
Ganesh
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Old   October 8, 2020, 18:11
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Yes, it is reasonably easy to switch. But it is a totally different model so it requires a little thought to get everything changed over.
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Old   October 8, 2020, 18:19
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Thank you very much.
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