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[LES] Reynolds stresses are lower than DNS

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Old   March 29, 2020, 13:10
Default [LES] Reynolds stress(w'w') is lower than DNS
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Hi,

I simulated a duct flow using Dynamic Smagorinsky model.
The simulation is completely converged.
The <w'w'> component of Reynlods stress is about half of DNS (you can see it in the attached image) while the mean streamwise velocity profile has a good agreement with DNS.

Anyone knows why?

Thank you.
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Last edited by Moreza7; March 29, 2020 at 17:15.
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Old   March 29, 2020, 14:29
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Quote:
Originally Posted by Moreza7 View Post
Hi,

I simulated a duct flow using Dynamic Smagorinsky model.
The simulation is completely converged.
The <w'w'> and <v'v'> components of Reynlods stress are about half of DNS (you can see it in the attached image) while the mean streamwise velocity profile has a good agreement with DNS.

Anyone knows why?

Thank you.



How did you compute the RMS?
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Old   March 29, 2020, 17:07
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How did you compute the RMS?
I used Code Saturne for simulation, calculated <w>^2 and <w^2> and used the following equation:

(\tau_{wall} is mean wall shear stress over 4 walls)
The other Reynolds stress components are pretty good.
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Old   March 29, 2020, 17:33
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I suggest to check further your RMS. The comparisons we did showed Code_Saturne overestimates the DNS peaks for the plane channel flow, see

https://www.researchgate.net/publica...mulation_codes


maybe the statistically averaged velocity is not well computed
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Old   March 30, 2020, 00:51
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Give some bleeding info about your simulation and that u are comparing with.
Document yr flow before you ask a question.

what Re? what resolution? whose dns? what is the exact geometry, channel or
rec/sq duct? which is the wall-normal and wall parallel component? if duct, where
in the cross section are the profiles from? are u including an estimate of the sgs
intensity in the stats? show a comparison with all three intensities.
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