## Fluids

#### Particle injections

• Prashank
Subscriber
I am injecting 64 particles from a inlet using the surface option . I have three outlets & I need to know how many particles escaped from each outlet .
1.is there any option to calculate that?

2 . I am also facing an another problem. My no of incomplete particles keep on fluctuating with the no of iteration . Like on 289th iteration
no of tracked particles= 64, escaped = 63 , incomplete = 1
But the on 300th iteration
No of tracked particles = 64, escaped =56, incomplete= 8
I don't why is this happening.( My model contains vortex formations , if that helps)
• Rob
Ansys Employee

Have a look at the results & particle positions: are any particles stuck in the recirculation/vortex zones? 64 is also quite low for statistical purposes: read up on stochastic tracking in the manual(s).

Have a look in the reporting options (monitors) and you should find a DPM Mass Escape. Assuming all the particles are the same size that should give you enough information. Alternatively use DPM Summary and review the data either as a histogram (Fluent) or via Excel or similar.

• hjubaer
Subscriber

My understanding is, the problem you (@Prashank) mentioned is not unusual. The number of incomplete particles will depend on how many steps with what step length factor/length scale Fluent is tracking your particles. If your particle is still trapped inside your domain (e.g. due to vortex formation) after the longest possible tracked length is reached, it will be declared incomplete. As your iteration progresses, there must be some fluctuations in the solution of the flowfield which will lead to fluctuations in the residence time of particles. Therefore, your number of incomplete particles will naturally vary as well, I suppose.

I would suggest that, you try increasing tracking parameters (e.g. Max Number of Steps) under your DPM settings, in order to let fluent track your incomplete particles to the end. This way you can account for the definite fate for all your injected particles.

I hope that helps.

Cheers
Hasan

• Prashank
Subscriber
Thanks mate for your valuable suggestion..I have tried looking into monitors but I couldn't find dpm mass escape ( can you tell me it's location ).I found some mass concentration but it's report only mass concentration not the count of particles.
2.Also the summary option in report is unavailable....
3. I did increase the max no of steps. It seems that the particles are trapped in between the vortex before their trajectories could complete. Is there any option I can found about the location of those particles..
• hjubaer
Subscriber

My guess is, you are running a steady-state simulation? If you are, then of course you are missing the particle current positions in your particle track summary.

If transient: Go to Particle tracks>Reporting>Current position and then you can add or remove variables that you want Fluent to report.

If steady state: Try Particle Tracks>Reporting>Step by step and then write the variables in a file

Either way, import the written file in excel and look at the residence time column first (column 1). May be sort the whole sheet according to decreasing residence time. So you now can see your culprits at the top. Column 2 through 4 should give you the particle positions (if the default order was not changed).

Cheers
Hasan