I am experiencing an issue with the DMP solver in MFIX on a virtual machine running Ubuntu 22.04.1 LTS, based on Windows 10. Initially, I can compile DMP solver and run the tutorial case without any problems. However, if I interrupt the simulation and attempt to restart the case,the time step size of the case increases rapidly, and the estimated remaining simulation time decreases sharply, I encounter errors that seem related to parallel processing. MFIX Version: 25.1.2
can you try with 26.1 release?
I tried version 26.1 ,and the exact same issue occurred
Do you have access to a Linux host? Or can you upload your case files so I can try this on Linux? I’d like to find out if this problem is related to WSL.
case.zip (22.6 KB)
We’ve been looking at this and I can reproduce your issue on Linux so it has nothing to do with WSL or even DMP - I get the same results running the job in serial mode
Here’s a plot of DT over a 200ms run:
Here’s the plot when I stop at 100 ms and restart:
There is a sharp increase in DT after the retart (but not immediately). We’re looking into this and will let you know what we find.
Thank you very much for your quick update and for confirming the issue on Linux. I really appreciate your detailed investigation and the plots you shared.
I’m glad to know the problem is not WSL/DMP related, and I’m looking forward to your further findings on the DT jump after restart. Please let me know if I can provide any additional data or test cases to help.
Thanks again for your support!
Still not 100% sure what’s going on but here’s some more data. I plotted residuals (fluid pressure and solids velocities), using a log-scale on the Y axis
Here’s what the residuals look like over a 100 ms run:
And here’s what I see if I stop after 50 ms then restart:
0-50ms:
50-100ms:
The issue is the turbulent length scale is not saved in the restart file. This is a bug, thank you for pointing this out. It will be fixed in the next point release. In the meantime, copy the two attached files to your project directory and rebuild the solver. Please let us know if this works for you. I cannot comment on whether a mixing length turbulence model is appropriate here nor if the turbulent length scale of 1m is appropriate, but this should address the time step change you are seeing upon restart.
read_res1.f (13.6 KB)
write_res1.f (7.9 KB)
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I am unable to download the two attachments included in your solution. Could you please send the two attachments to my email address: [deleted]? Thank you very much!
What happens when you click the download link? I’ll try to fix it if you tell me what the error is.
The picture shows “This page cannot be accessed”.
Interesting, the error is “Connection timed out”, not a permissions issue. I’ll try to look into this. In the meanwhile I will email you the files.