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April 17, 2021, 15:58 |
Diverging solution on HPC cluster
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#1 |
New Member
Priyanka Gautam
Join Date: Apr 2015
Location: India
Posts: 4
Rep Power: 11 |
Hi,
I am running Reef3D on an HPC cluster, but unfortunately ever since I had updated Reef3D to the latest version, the solutions are diverging (values exceeding the critical velocity). Interestingly, the same control files are running normally on a 4-core PC. Any suggestion in this regard will be greatly appreciated! Thanks in advance. |
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April 17, 2021, 18:57 |
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#2 |
Super Moderator
Hans Bihs
Join Date: Jun 2009
Location: Trondheim, Norway
Posts: 403
Rep Power: 19 |
Thanks for the feedback. What type of simulation are you running?
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April 19, 2021, 07:35 |
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#3 |
New Member
Priyanka Gautam
Join Date: Apr 2015
Location: India
Posts: 4
Rep Power: 11 |
Hello, sir. Thank you for the prompt response.
I am simulating open channel flow around a cylinder in a rectangular domain. The umax parameter is exponentially increasing with each time step, crossing a value of 500 m/s. |
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April 19, 2021, 08:19 |
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#4 |
Senior Member
Arun Kamath
Join Date: Nov 2014
Location: Trondheim, Norway
Posts: 265
Rep Power: 14 |
Hi Priyanka,
could you please share your input files so that we can take a closer look?
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Arun X years with REEF3D |
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April 19, 2021, 08:32 |
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#5 |
New Member
Priyanka Gautam
Join Date: Apr 2015
Location: India
Posts: 4
Rep Power: 11 |
Hi Arun
I am attaching the control files. |
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April 19, 2021, 08:37 |
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#6 |
Super Moderator
Hans Bihs
Join Date: Jun 2009
Location: Trondheim, Norway
Posts: 403
Rep Power: 19 |
When you are running the case on the laptop, do you use the same mesh width?
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April 19, 2021, 09:04 |
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#7 |
New Member
Priyanka Gautam
Join Date: Apr 2015
Location: India
Posts: 4
Rep Power: 11 |
While running on the laptop, I have kept the same mesh width.
PS: All the functions (except the M10 parameter), are kept the same in both control.txt and ctrl.txt files. |
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April 19, 2021, 15:37 |
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#8 |
Senior Member
Arun Kamath
Join Date: Nov 2014
Location: Trondheim, Norway
Posts: 265
Rep Power: 14 |
I am not sure why it works locally and fails on the cluster, but the solution is most probably to avoid using N 40 6. This crashes cases for me locally as well with open channel flow.
Use N 40 3 and the problem should be solved.
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Arun X years with REEF3D |
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April 19, 2021, 18:04 |
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#9 |
Super Moderator
Hans Bihs
Join Date: Jun 2009
Location: Trondheim, Norway
Posts: 403
Rep Power: 19 |
Yes, Arun is correct, N 40 6 can be less stable than N 40 3. But his should be independent of the processor count. We are currently looking in to the matter.
Another idea: maybe you did not make clean the previous build on your HPC cluster before you compiled the newest version? Maybe you have a go, make clean and then compile again? |
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April 22, 2021, 06:09 |
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#10 |
Senior Member
Arun Kamath
Join Date: Nov 2014
Location: Trondheim, Norway
Posts: 265
Rep Power: 14 |
A small update. With the latest version of the model, N 40 6 seems to work fine (but I would still advice caution while using it).
I do notice though that the cylinder you have in the domain has about the same diameter as the grid size. I would advice using a stretched grid to include more cells around the structure. And finally something that might just solve the cluster problem, add M 20 2 to control.txt (Since I cant really reproduce the error, I am limited to looking all possible options, one by one) Did you see a change after making a fresh compilation of the latest version?
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Arun X years with REEF3D |
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April 22, 2021, 08:08 |
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#11 |
Super Moderator
Hans Bihs
Join Date: Jun 2009
Location: Trondheim, Norway
Posts: 403
Rep Power: 19 |
We have tested your files with 24 cores. Everything works, so I think it is a compilation problem. As I wrote before:
maybe you did not make clean the previous build on your HPC cluster before you compiled the newest version? Maybe you have a go, make clean and then compile again? |
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Tags |
cfd analysis, convergence, error, hpc cluster, reef3d |
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