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-   -   Particle tracking prob, urgent. (http://www.cfd-online.com/Forums/cfx/114417-particle-tracking-prob-urgent.html)

sakurabogoda March 11, 2013 01:21

Particle tracking prob, urgent.
 
Dear All,

I am modeling a particle tracking simulation by LES.

In particle digestions I can see following,

| Particle Fate Diagnostics |
+--------------------------------------------------------------------+
| Particle type | Fate type Particles |
+--------------------------------------------------------------------+
| Particle 8um | Entered domain : 1 |
| | Continue from last time step : 885 |
| | Waiting for next time step : 885 |
| | Exceeded integration limit : 1 |
+--------------------------------------------------------------------+
| Particle 5um | Entered domain : 1 |
| | Continue from last time step : 883 |
| | Waiting for next time step : 884 |
+--------------------------------------------------------------------+
| Particle 2um | Entered domain : 1 |
| | Continue from last time step : 877 |
| | Waiting for next time step : 876 |
| | Exceeded integration limit : 2 |
+--------------------------------------------------------------------+
| Particle 1um | Entered domain : 1 |
| | Continue from last time step : 876 |
| | Waiting for next time step : 876 |
| | Exceeded integration limit : 1 |
+--------------------------------------------------------------------+
| Particle 10um | Entered domain : 1 |
| | Continue from last time step : 913 |
| | Waiting for next time step : 913 |
| | Exceeded integration limit : 1 |
+--------------------------------------------------------------------+

But I have given particle numbers as,

1um- 100 particles, 2um- 100 particles, 5um-200 particles, 8um-300 particles and 10um-300 particles.

01. Then why no. of particles shows around 800-900 in each step? But at every step I can see mass flow rate is same to which I assigned.
02. At many time steps particles at "Exceeded integration limit" is present, so within 10000 steps, all particles will reach to this fate and nothing will exit. Am I correct?
03. I can see in output file chart, "Particle Source Change Rates" curves are having more fluctuations (1.00-0.001 variable value range). Is my particle tracking diverging (considering this chart)?


Pls help me.

sakurabogoda March 11, 2013 22:11

Dear All,

I guess my problem is due to Iteration frequency.

I have used:

1st iteration for particles =1
Iteration frequency =300

But documentation says,
"If the continuous phase reaches its convergence criterion before the particle calculation reaches its own convergence criterion, then the code automatically overrides the value specified for the iteration frequency, and starts to track the particles on every iteration."

This is what happening in my simulation, after 1st iteration at every iteration it release particles.

Can anybody make me a suggestion to overcome from this?

I am really stuck on this.


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