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'sample' utility for 'U' yields different results for simple-scotch-etc. |
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#1 |
Senior Member
Canakkale Dardanelspor
Join Date: Aug 2012
Posts: 135
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Hi
== 1 == For a lowest-effort-possible grid using LES-pisoFoam, using sample utility for 'U' seems yielding different results giving the same coordinates for:
== 2 == Actually 2 and 3 (i.e. simple and hierarchial) give identical results. Thus, 1, 2-3 and 4 produce the different results. == 3 == Let me also note that, only 2 time-steps I run: 0.001 and 0.002 secs. == 4 == The lowest-effort case files are given in the following link: http://speedy.sh/bnAQM/1-test-to-send-away.zip == 5 == The obtained results (for the given 'sampleDict' inside the above case files) can be seen from the following link: http://speedy.sh/NTzGr/Results.zip == 6 == Assuming the sample utility gives the exact answer from the above computational domain, could anyone please tell me what would be the reasoning behind these different answers despite the solution settings are the same? Also note that the cases are not converged at all. But, I attempt to understand how the parallelization would affect the results obtained from the same setting cases? e.g. when the simulation cases are numerically converged (e.g. according to the final residual of pressure) , should I expect that sampling of U will give the same results for all types of parallelization methods? == 7 == Many thanks for any comment and time being spent. |
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#2 |
Retired Super Moderator
Bruno Santos
Join Date: Mar 2009
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Greetings HakikiCanakkaleli,
Once the solution is converged, the results should be nearly identical, but not necessarily 100% identical. As for the several decomposition methods: running in parallel sometimes requires changing the parameters in "fvSchemes" and "fvSolution", because what works fine in serial mode, doesn't mean that it will run fine in parallel mode. Here's an example (I couldn't find another one I was looking for): http://www.cfd-online.com/Forums/ope...lllimited.html And I'm unable to download the files from that website. Can you share the files via Dropbox, Google Drive, SkyDrive or something similar? Best regards, Bruno
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#3 |
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Canakkale Dardanelspor
Join Date: Aug 2012
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Many thanks Bruno for your time and explanations,
Here the files: " == 4 == The lowest-effort case files are given in the following link: https://drive.google.com/file/d/0BzV...it?usp=sharing == 5 == The obtained results (for the given 'sampleDict' inside the above case files) can be seen from the following link: https://drive.google.com/file/d/0BzV...it?usp=sharing " |
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#4 | |
Retired Super Moderator
Bruno Santos
Join Date: Mar 2009
Location: Lisbon, Portugal
Posts: 10,978
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Hi HakikiCanakkaleli,
I've finally managed to have a look into your files, but I haven't managed to do any tests with them, due to insufficient time... But here's what I've seen that might be the reason for the big differences in results:
Best regards, Bruno
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