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DPM in a Cyclone

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Old   January 13, 2009, 12:26
Default DPM in a Cyclone
  #1
francesca
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hello!!!

I have a problem with DPM in a cyclone.

My simulation run with RSM model and reach the convergence with second order discretization and gravity off.

Now my problem is this: i had create tre injections with 10^-6, 10^-4, 10^-3 diameters and i'll aspect that the injection with bigger diameter have a number of escape less than the other, but it is't so. Why???

Another question, now my boundary condition is "trap" but so the particle disappear from the domain, i would that they slip along the wall and simulate the possibility that the particle can carry out again.

Is it possible?

thanks in advance!!!!!

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Old   January 13, 2009, 13:29
Default Re: DPM in a Cyclone
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Allan Walsh
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Use "reflect" for wall DPM boundary conditions, with appropriate reflection parameters.
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Old   January 14, 2009, 04:36
Default Re: DPM in a Cyclone
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francesca
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Tanck You very much, Allan!

I'll try with small reflection parameters.

For the other problem wath do you think? I tried to turn on the gravity but the result not chance.
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Old   January 14, 2009, 11:29
Default Re: DPM in a Cyclone
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francesca
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Hi Allan, i have a question again, i'm sorry!!!

Is possible display only the particle tracks that are defined "incomplete"?

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Old   January 14, 2009, 13:22
Default Re: DPM in a Cyclone
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Allan Walsh
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Your problems with the particles and collection efficiencies are likely related. Once you choose appropriate conditions for wall reflection parameters, then the results may look more reasonable. (Note that parameters you choose for the normal and tangential reflection coefficients should be representative of the type of particle. Particles like sand will bounce off the walls with more energy than soft or partially liquid particles.)

Do you have a trap boundary condition? Typically, particles will be separated by removing them from the bottom of the cyclone. You can use a trap condition to avoid them from being re-entrained. And, if you don't trap the particles they may exceed the time limit you have set and you will get an "incomplete" result for the particle.

Since the incomplete particles are ones that stay in the domain too long (time step multiplied by the number of steps) you can plot the particle paths coloring them by time. If the particles are in the domain for an unreasonably long time (say a minute), then there is probably a problem with your boundary conditions.

If you really want to see the incomplete particles, turn off the autorange in the color scale of particles and set the minimum to a fairly large time value.

Good luck with the simulation.
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Old   January 15, 2009, 09:53
Default Re: DPM in a Cyclone
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francesca
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Hi Allan, you are very kind and very fast in the answer.

I had set reflection parameters as 0 for both normal and tangential coefficient. Doig so ( I Think ) the bounce is anaelastic and if the particle is too heavy for the gas velocity they will slip along wall. I'm wrong!?

I had set "trap" condition for the bottom.

Now i have this result: for the diameters of 10^-3 m - escape = 0 - trap = 167 - incomplete = 11

for the diameters of 10^-6 m - escape = 40 - trap = 121 - incomplete = 17

The incomplete tracks are near the bottom,can I consider them as "trap"? I should smooth the mesh near the bottom, right? What do you think, could I be satified?

Thanks, Thanks again

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Old   January 15, 2009, 17:54
Default Re: DPM in a Cyclone
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Allan Walsh
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Yes, you are correct in that the zeros for reflection coefficients would give inelastic behavior. This might be more typical of liquid drops. This boundary condition will slow down the particles and many of them could be expected to be incomplete - or that they would eventually be trapped given enough calculation time.

I don't think smoothing the mesh near the bottom would have much effect.

Looks like you are nearly finished!
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Old   January 16, 2009, 11:27
Default Re: DPM in a Cyclone
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francesca
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Yes, i'm happy.

This is my first simulation, there have been periods of frustration, but i finally finished.

Thank Yuo very much for all!!!

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Old   May 18, 2010, 01:17
Default Two Phase in cyclone
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roghi
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Dear all;
I want to simulate two phase(air-water) flow in the cyclone. Air is continous phase.
At first I need experimental data.Please help me if you have any?!
And I do not know what should be checked to validate the simulation.Please Help.
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