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-   -   how to calculate rms velocity fluctuation after runtime (http://www.cfd-online.com/Forums/openfoam-post-processing/105878-how-calculate-rms-velocity-fluctuation-after-runtime.html)

nati August 11, 2012 09:44

how to calculate rms velocity fluctuation after runtime
 
Hello ,

I used les model but I cant calculate rms velocity fluctuations or reynolds stress tensor :(. Does anyone know how we can calculate rms velocity fluctuations during post-processing?

Thanks so much,:)

nichkoohi August 14, 2012 17:32

uprime calculation
 
hi nati
after your solution is terminated, just write in terminal window( your runs directory): uprime
the velocity fluctuation is calculated and save on your folder runs.
see page 93 of openfoam userguide.
nichkoohi@yahoo.com

nati August 14, 2012 20:28

Quote:

Originally Posted by nichkoohi (Post 377109)
hi nati
after your solution is terminated, just write in terminal window( your runs directory): uprime
the velocity fluctuation is calculated and save on your folder runs.
see page 93 of openfoam userguide.
nichkoohi@yahoo.com


hi,

tnx! In uprime, it has been hypothesized that rms velocity fluctuations in diffrent directions are same and equal with sqrt (2/3k)! :(

Hanzo November 9, 2012 02:40

Hi,

I also dealt with that problem. I wrote a small tool called

postAverageTurbulenceFields

which iterates over all the timesteps in your directory and writes out the whole set of turbulence properties

k, eps, nu_eff, R, R_eff, Umean, UPrime2Mean

So far it works for LES turb models but modification to RAS turb models should be easy. You still need that tool?

it's basically an extension of the tool postAverageFields by eelcovv
http://www.cfd-online.com/Forums/ope...rocessing.html

nati December 9, 2012 10:13

Dear Hanzo,
Pardon me for being late in answering you.:(
Yes , I still need it so much.
can you help me on this issue ?
Regards,
Nati



Quote:

Originally Posted by Hanzo (Post 391147)
Hi,

I also dealt with that problem. I wrote a small tool called

postAverageTurbulenceFields

which iterates over all the timesteps in your directory and writes out the whole set of turbulence properties

k, eps, nu_eff, R, R_eff, Umean, UPrime2Mean

So far it works for LES turb models but modification to RAS turb models should be easy. You still need that tool?

it's basically an extension of the tool postAverageFields by eelcovv
http://www.cfd-online.com/Forums/ope...rocessing.html


vonboett February 5, 2013 06:50

Hi Hanzo, I am interested in your tool, too. I work with the hybrid LES / RANS models of the LEMOS extensions and I have to think well about how to visualize the turbulent fluctuations due to LES and RANS seperateley. I would be happy if I could have a look at your code...

Hanzo February 7, 2013 09:42

Quote:

Originally Posted by nati (Post 396514)
Dear Hanzo,
Pardon me for being late in answering you.:(
Yes , I still need it so much.
can you help me on this issue ?
Regards,
Nati

Quote:

Originally Posted by vonboett (Post 406079)
Hi Hanzo, I am interested in your tool, too. I work with the hybrid LES / RANS models of the LEMOS extensions and I have to think well about how to visualize the turbulent fluctuations due to LES and RANS seperateley. I would be happy if I could have a look at your code...

Sorry for the late answer. Please find my code here:

http://www.cfd-online.com/Forums/ope...ields-les.html

Let me know if it works :)

Best,
Hanzo


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