question on “warning：0.2640% of the total discrete phase mass was not tracked”

- January 31, 2023 at 12:33 pm
  
  lu jia
  Subscriber
  
  When using DPM model ，“Warning：0.2640% of the total discrete phase mass was not tracked for the expected residence time” appears.
  I have increased the max number of DPM steps to 20000 in unsteady tracking mode.And the time step of transient simulation is 0.0001s.I wonder whether it is acceptable to the simulation if there exists warnings every time step but the error only within 0.1% at most of time.
  Thanks advance.
- January 31, 2023 at 1:10 pm
  
  Rob
  Ansys Employee
  
  It's probably OK. You'll have a few particles stuck in a recirculation zone somewhere. If you're needing 20,000 steps in transient I'd be checking the time step though.
  - February 1, 2023 at 4:35 am
    
    lu jia
    Subscriber
    
    Thanks. If I change the time step to 1e-5 s, the warning would rarely appear. But it take a few days more to simulate the case. If the result is accpetable(that is, warning appears but it shows relatively low percent), I'd like to take less time to simulate.
- February 1, 2023 at 9:59 am
  
  Rob
  Ansys Employee
  
  I'm not allowed to give an answer to that: one of several rules I have to (and do) adhere to. So, in your case can you afford to lose track of virtually no mass for a tiny amount of time? How does that mass compare to any other assumptions you're making?
  - February 1, 2023 at 10:53 am
    
    lu jia
    Subscriber
    
    OK, thanks for your tips, I will rethink the question in the situation of the case.

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