Dpm model, setting particle number

wagnerqb · March 22, 2013, 13:40

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, 05:11

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, 06:01

Quote:

Originally Posted by Yanlong Li

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, 06:06

May I know your "flow time step" ?

jthiakz · March 23, 2013, 06:32

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, 14:35

Quote:

Originally Posted by Yanlong Li

May I know your "flow time step" ?

Time step: 1e-4.

wagnerqb · March 23, 2013, 14:38

Quote:

Originally Posted by jthiakz

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, 21:06

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

March 22, 2013, 13:40	Dpm model, setting particle number	#1
wagnerqb New Member Wagner Queiroz Barros Join Date: Jan 2013 Posts: 13 Rep Power: 13	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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March 23, 2013, 05:11		#2
Yanlong Li Member Yanlong Li Join Date: Jan 2013 Location: BeiJing Posts: 47 Rep Power: 13	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.

March 23, 2013, 06:06		#4
Yanlong Li Member Yanlong Li Join Date: Jan 2013 Location: BeiJing Posts: 47 Rep Power: 13	May I know your "flow time step" ?

March 23, 2013, 06:32		#5
jthiakz Member Thiagu Join Date: Oct 2012 Location: India Posts: 60 Rep Power: 13	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

March 23, 2013, 21:06		#8
Yanlong Li Member Yanlong Li Join Date: Jan 2013 Location: BeiJing Posts: 47 Rep Power: 13	Try to set "particle time step" as (76900/9000)^(-1) = 0.117 and keep the "flow time step" as 1e-4.