CFD Online Discussion Forums

CFD Online Discussion Forums (https://www.cfd-online.com/Forums/)
-   FLUENT (https://www.cfd-online.com/Forums/fluent/)
-   -   Fluent Iterating very slow (https://www.cfd-online.com/Forums/fluent/226631-fluent-iterating-very-slow.html)

Sherif.farrag May 3, 2020 06:34

Fluent Iterating very slow
 
Hi,

I did 2D simulation on Ansys Fluent. iterating was very smooth and one iteration takes ~1sec as the mesh has 80 thousands elements.
I did the same model but 3D I got 6 Million elements and one iteration takes ~15 minutes. is that normal ? knowing that thousands of iterations are needed from my 2D experience with the model!
I have Intel Core i5 with 8 Gb Ram. Using parallel processing with 4 cores and single precision instead.
The model is a simple supersonic flow over rocket nozzle.
Any ideas? Is that normal?

vinerm May 3, 2020 16:12

Speed of calculation
 
For a 6 million cell count (assuming you mean cell count by element because element terminology is not used in FVM or Fluent), it in itself is a miracle that you are able to run it at all on an 8GB RAM machine. For a 8 GB RAM, if you are running single phase, turbulent flow, limit is 2 million for an optimum speed. 6 million cell count requires minimum 24 GB RAM for a optimum run. Speed is dependent on RAM speed and processor speed.

Sherif.farrag May 3, 2020 21:29

Thanks Vinerm for your help.
I've tried my friend's machine. It's Intel i7 with 16Gb Ram. it worked a lot faster. now one iteration takes ~6sec.
As you know now I have to take the results from my friends after finishing.
What is the best way to do that?
Taking the whole folder? or exporting data and open it with my CFD-Post?
Taking in consideration that he is using newer Ansys version than mine.
Also take in consideration that some times when I'm doing export a result and open in in CFD post independently it gives missing mesh error!
So, What is the best way to take the results?

vinerm May 5, 2020 09:20

Case
 
If it is steady-state, then just take final case and data files and open those in CFD-Post. CFD-Post can open newer version data files as well. Mesh error comes only if case file is not available in the same directory. User does not need to load case file in CFD-Post but it must be available in the directory with the same name as that of data file that user loads in CFD-Post.

If it is transient, then better to export cdat files and a final set of case and data files.


All times are GMT -4. The time now is 21:28.