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-   -   Dpm model, setting particle number (http://www.cfd-online.com/Forums/fluent/115065-dpm-model-setting-particle-number.html)

wagnerqb March 22, 2013 14:40

Dpm model, setting particle number
 
Hi everybody,

I have to model a particle transports, and I am having trouble with the particle numbers. I am using a surface injection to inject the particles in my problem, the surface has 9000 faces, so is injected 9000 particles each time step.

Thinking in my problem:
Particle Diameter 0.001 m.
Particle volume (considering a spherical particle) 5.233e-10 m3
Injection flow. 0.1 kg/s
Particle density 2600 kg/m3

So using the particle density:
Particle mass 1.3e-6 kg

So per second have to be injected 76900 particles where is the rest of these particles?

Why if I change the time-step the number of particles is changed?

Please it is very important to understand better this model. If anyone has a suggestion I would be really glad.

Yanlong Li March 23, 2013 06:11

The DPM has its own "particle time step", you can specify the value by the total mass flow rate, particle diameter, density, et al. If you did not changed the paritcle time step, it would be the same as "flow time step" by default.

wagnerqb March 23, 2013 07:01

Quote:

Originally Posted by Yanlong Li (Post 415836)
The DPM has its own "particle time step", you can specify the value by the total mass flow rate, particle diameter, density, et al. If you did not changed the paritcle time step, it would be the same as "flow time step" by default.

Ok, I can understand it, but I cannot control the number of particles in my simulation. According to my example above, There would be 76000 particles per second in my simulation, but it does not happens.

Yanlong Li March 23, 2013 07:06

May I know your "flow time step" ?

jthiakz March 23, 2013 07:32

In the fluent output window can you able to see the same no of particle numbers. if you can show DPM iteration output. it's better

wagnerqb March 23, 2013 15:35

Quote:

Originally Posted by Yanlong Li (Post 415845)
May I know your "flow time step" ?

Time step: 1e-4.

wagnerqb March 23, 2013 15:38

Quote:

Originally Posted by jthiakz (Post 415848)
In the fluent output window can you able to see the same no of particle numbers. if you can show DPM iteration output. it's better

I could see that report, and it was useful.

Just one question, how can I specify a surface that collects the information of every particle that passes through it?,

Example.
I need to crate a graph with de particle residence time versus the number of particles that is crossing my surface. How do I do it?

Thanks.

Yanlong Li March 23, 2013 22:06

Try to set "particle time step" as (76900/9000)^(-1) = 0.117 and keep the "flow time step" as 1e-4.


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