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-   -   Large transient ".trn" files when doing time average (https://www.cfd-online.com/Forums/cfx/155070-large-transient-trn-files-when-doing-time-average.html)

dtmith June 24, 2015 10:16

Large transient ".trn" files when doing time average
 
Hello,

This will show how little I understand CFX's output file structure :)

I'm running some transient simulations. When I do NOT enable any transient averaging, the .trn file size is around 1.5-1.7GB, which is fine. When I enable transient averaging through transient statistics, say from time step 200 to 300, ALL the .trn files, even those for timesteps smaller than 200 are much much larger, 6 to 7GB.

This is rather problematic as I'd like to output transient files frequently so I can see the time development of flow structures.... but I'd also like a transient average over a certain period of time to get a time averaged flow field.

Even if I set the "Transient Result" "Option" to "Essential" the files are still huge.

Is there something obvious I'm missing? Is there something simple I can do to get the .trn file size down when also doing transient statistics? I would have thought transient statistics should have no effect on individual .trn files, especially those before or after the statistics even take effect.

singer1812 June 24, 2015 14:23

I dont use transient statics option in CFX (i do most of that work outside of CFX) but I assume they store the statistics in the trn files.

Try changing from Essential to selected variables and choose a very small select subset (perhaps just u,v,w). If this doesnt reduce the size of the trn files, then the entire reason is due to your transient statistics, and you probably are doing statistics on too many variables to keep the output small.

dtmith June 28, 2015 09:06

If I do "Selected Variables" with only U,V,W, the files are still 2.7+ GB which is smaller than "Standard" but is still far too large and still much larger than when I don't do transient statistics at all (and not useful! I need more than just U,V,W).

Is there no way to tell it to simply not save transient statistics in .trn files? Surely it can just save them in the final .res file rather than in individual .trn files (especially those that are before I even asked it to start averaging)?


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