[priyankaiitb]

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.

[valgrinda]

Thanks for the feedback. What type of simulation are you running?

[priyankaiitb]

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.

[kamath]

Hi Priyanka,
could you please share your input files so that we can take a closer look?

[priyankaiitb]

Hi Arun

I am attaching the control files.

[valgrinda]

When you are running the case on the laptop, do you use the same mesh width?

[priyankaiitb]

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.

[kamath]

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.

[valgrinda]

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?

[kamath]

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?

[valgrinda]

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?