Learning Forum

[oobiols]

Hello everybody.

I am trying to run a Compressible (Ma=0.2) flow case around an object using ANSYS Fluent v18. I have been succesful running Compressible Flow around a 2D and 3D cylinder. Now, however, I want to run a much larger case: the case file (fluentcase.cas) is almost 17 GB.

I can read the case and I can set the simulation up. I choose the time discretization, the spatial discretization, the CFL number, etc., and I even initialize the case. However, when I select 'calculate' and the solver starts computing the first iteration, I get the following error before the first iteration is computed:

>   iter  continuity  x-velocity  y-velocity  z-velocity      energy

Error:  received a fatal signal (Segmentation fault).

 

Error:  received a fatal signal (Segmentation fault).

Error Object: #f

 

     time/iter

 

After several days, I can not find the source of the problem. I am approaching it as a steady problem just to do a first assessment of the solution and see if Fluent - even if it is not the right answer - can handle the case. Can it be a memory issue?

Help much appreciated. Thank you for reading.

[Karthik R]

Hello Segmentation fault could be due to multiple reasons. Here are some of my thoughts which might help you debug your model.

If you want to isolate memory issues, you could try to run a simple case of steady incompressible laminar flow, with energy equation turned off. If your case runs without any errors, there might be some other issues with your set-up that are causing segmentation errors.
You could, perhaps, reduce the mesh density to check if it is the memory that is causing the issue. Are you running the case locally? What is your RAM? Would you have access to a high memory system?

Make sure all your boundary and initial conditions are physical.

Check your mesh quality, especially skewness. Even a small number of bad cells can cause issues.

I hope you are not using any UDFs. If you are, I would strongly recommend that you try to trim your case without the UDF. Please test your UDF on a simpler problem.

Which turbulence flow model are you using? Have you used the correct mesh according to your model?

I understand that these suggestions are very broad and some one them might not be applicable to your case. I hope this helps.

Best regards Karthik

[oobiols]

Thanks, that helped a lot. It was a RAM memory issue. Now it is working, thanks.