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-   -   Any library to calculate <u'> ? (http://www.cfd-online.com/Forums/openfoam-post-processing/115099-any-library-calculate-u.html)

atmcfd March 23, 2013 19:15

Any library to calculate <u'> ?
 
Hi all,

I need to calculate u' ( i.e. (Umean - U) ) for all times and then want to calculate average <u'> . All this is needed for a simulation already completed ..i.e as a postprocessing job. Does OpenFOAM have any libraries to do this?

Thank you.

Atm

gschaider March 24, 2013 06:55

Quote:

Originally Posted by atmcfd (Post 415922)
Hi all,

I need to calculate u' ( i.e. (Umean - U) ) for all times and then want to calculate average <u'> . All this is needed for a simulation already completed ..i.e as a postprocessing job. Does OpenFOAM have any libraries to do this?

Thank you.

Atm

Hm. u' I'd do with funkySetFields (assuming you mean with Umean "volume weighted average"):

funkySetFields -create -field Udev -time 0: -expression "U-sum(vol()*U)/sum(vol())"

For averaging those I must admit I'm currently not aware of a readymade solution

atmcfd March 24, 2013 14:33

Bernhard,

By UMean, I refer to the "UMean" file which is the time averaged velocity which I get in the time step folder after the fieldAveraging library is used. So I want to do U (file in the folder) - UMean to get u' , v' and w' for every time step.

Then , if possible obtain time averaged quantities <u'>, <v'> and <w'>.

Can funkyset do this?

Thanks !

Atm

gschaider March 24, 2013 17:58

Quote:

Originally Posted by atmcfd (Post 416055)
Bernhard,

By UMean, I refer to the "UMean" file which is the time averaged velocity which I get in the time step folder after the fieldAveraging library is used. So I want to do U (file in the folder) - UMean to get u' , v' and w' for every time step.

This is trivial: if there is a field-file of that name in the time-directory then FSF can access it. The expression is simply "U-UMean"

Quote:

Originally Posted by atmcfd (Post 416055)
Then , if possible obtain time averaged quantities <u'>, <v'> and <w'>.

Can funkyset do this?

Not 100% sure: it might be possible if the expression is read from a dictionary (instead of the command line) together with storedVariables. But I'd have to test that


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