Large transient ".trn" files when doing time average

dtmith · June 24, 2015, 11:16

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, 15:23

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, 10:06

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)?

June 24, 2015, 11:16	Large transient ".trn" files when doing time average	#1
dtmith New Member Join Date: Mar 2015 Posts: 9 Rep Power: 11	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.

Similar Threads
Thread	Thread Starter	Forum	Replies	Last Post
y+ and u+ values with low-Re RANS turbulence models: utility + testcase	florian_krause	OpenFOAM	114	August 23, 2023 06:37
Micro Scale Pore, icoFoam	gooya_kabir	OpenFOAM Running, Solving & CFD	2	November 2, 2013 14:58
mixerVesselAMI2D's mass is not balancing	sharonyue	OpenFOAM Running, Solving & CFD	6	June 10, 2013 10:34
Upgraded from Karmic Koala 9.10 to Lucid Lynx10.04.3	bookie56	OpenFOAM Installation	8	August 13, 2011 05:03
critical error during installation of openfoam	Fabio88	OpenFOAM Installation	21	June 2, 2010 04:01

June 24, 2015, 15:23		#2
singer1812 Senior Member Edmund Singer P.E. Join Date: Aug 2010 Location: Minneapolis, MN Posts: 511 Rep Power: 21	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.

June 28, 2015, 10:06		#3
dtmith New Member Join Date: Mar 2015 Posts: 9 Rep Power: 11	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)?