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Dpm model, setting particle number

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Old   March 22, 2013, 14:40
Default Dpm model, setting particle number
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Wagner Queiroz Barros
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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.
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Old   March 23, 2013, 06:11
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Yanlong Li
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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.
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Old   March 23, 2013, 07:01
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Quote:
Originally Posted by Yanlong Li View Post
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.
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Old   March 23, 2013, 07:06
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Yanlong Li
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May I know your "flow time step" ?
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Old   March 23, 2013, 07:32
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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
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Old   March 23, 2013, 15:35
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Quote:
Originally Posted by Yanlong Li View Post
May I know your "flow time step" ?
Time step: 1e-4.
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Old   March 23, 2013, 15:38
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Quote:
Originally Posted by jthiakz View Post
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.
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Old   March 23, 2013, 22:06
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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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