Learning Forum

[yfeng4]

I see some warnings as below. My understanding is that that means the I should increase the maximum number of time steps to compute a single particle trajectory in a single fluid time step. However, I have 500 as the maximum particle time steps, and 5e-4s as the particle time step while 0.01 as the fluid time step. I think it should be able to finish all the particle tracking in each fluid time step. I am confused about how I should solve this problem. Thank you very much. Best regards.

 

"Advancing DPM injections ....

number tracked = 46080, escaped = 14, aborted = 0, trapped = 2072, evaporated = 0, incomplete = 1162, incomplete_parallel = 0

Parallel particle tracking concurrency: 21%

 

WARNING: 2.6971% of the total discrete phase mass was not tracked for the expected residence time:

0.00688 s less on a mass-weighted average (which is 3.2519% of their total age or 68.8441% of the last time step).

You may be able to reduce this discrepancy by changing the tracking parameters, that is,

increasing the maximum number of time steps used to compute a single particle trajectory.

 

Flow time = 0.3599999248981476s, time step = 36"

[Karthik Remella]

Hello,

The reason you might be seeing this warning is because of your time step size. For particles with very high velocity, the number of integration steps used are insufficient to track the particles for entire length of the flow time step. You can try reducing the time step size or increasing the number of steps in DPM model panel.

In order for us to fully understand the issue, could you please provide us with some more details about your geometry, mesh, and model?

Thank you.

Best Regards,

Karthik

[DrAmine]

To add to the comments of Karthik, Fluent wants to tell you that  the 1162 unsteady particle parcels that did not escape or were trapped are behind in time by 68 % of the whole time step and these particles were not be able to be tracked over the whole time step as the maximum number of steps has been reached. To remedy this follow what Karthik already mentioned .

[yfeng4]

Hi Abenhadj and Kremella,

thank you very much for both of your comments. The problem solved! Best regards

 

[DrAmine]

Good to know that it works now. Thanks for highlighting that the issue has been resolved.

[Karthik Remella]

Hello
Glad to be of help.
Good luck with your modeling.

Best Karthik

[MohAgha1]

Dear yfeng4; Can you share your experience of how did you solve this problem?

I have the same warning and it continues till causing divergence in the solver when the incomplete particle % reaches 10%

I applied the solutions listed above of decreasing the dpm time-step and increasing the number of steps, but unfortunately didn't work!

Thanks in advance;

Mohamed

[DrAmine]

Please create a dedicated thread so that all of us can chime in. Do not forget to add some details.

[MohAgha1]

Dear Amine; I don't understand what do you mean by "dedicated". I commented on the post because I had the same problem of the mentioned warning of DEM particles tracking. I tried the approved solution of Kremella, but nothing changed I still have the same warning which leads to divergence in the solution

I am asking yfeng4 if he/she applied another method which can solve the problem or any other recommendations

Regards;

Mohamed

[DrAmine]

Hi Mohamed,

Are you using length scale or length ratio under tracking parameters? Can you copy and paste your error message here?

[yfeng4]

Hi Mohamed,

I guess Amine means that you can create a separate discussion and state your question with detailed Fluent setup specs.

In any case, I solved the problem by doing two things:

(1) Lower the fluid time step, and

(2) Increase the maximum number track particles. 

Hope this will help! Best,

[sanusi]

Hi  everyone,

I'm currently faced with a similar problem in IC engine simulation as seen below. Also, I've tried to reduce the time step both its keeps coming.

WARNING: 0.0007% of the total discrete phase mass were behind in time by, on mass-weighted average, 9.57e-06 s, which is 2.4327% of their total age or 78.0911% of the last time step

 

Deleted 107 particles in injection injection-0 with total mass 1.101314e-14 kg

 

Deleted 41934 particles in injection injection-0 with total mass 5.303207e-15 kg

 

Deleted 1 particles in injection injection-0 with total mass 6.688036e-17 kg

 

Deleted 56 particles in injection injection-0 with total mass 2.040446e-18 kg.

please come to my aid.

 

[DrAmine]

Please create a new thread for your question and add as much information on your case as you can.