CFD Online Logo CFD Online URL
www.cfd-online.com
[Sponsors]
Home > Forums > Software User Forums > OpenFOAM > OpenFOAM Post-Processing

Total Reynolds Stress and Turbulence Energy Spectrum of LES

Register Blogs Members List Search Today's Posts Mark Forums Read

Like Tree3Likes
  • 3 Post By GiulioS

Reply
 
LinkBack Thread Tools Search this Thread Display Modes
Old   July 10, 2013, 19:16
Default Total Reynolds Stress and Turbulence Energy Spectrum of LES
  #1
New Member
 
realM
Join Date: Jan 2013
Posts: 3
Rep Power: 13
sanysaly is on a distinguished road
Hi,
I am doing LES with pisoFoam. My questions that may be useful as post-processing tools and/or as a utility for validation of model are:
1- How can we calculate the Total Reynolds Stress? Based on thread (http://www.cfd-online.com/Forums/ope...tml#post342243),
We just need to “UPrime2Mean + RMean” (respectively resolved + SGS parts) to get the full stresses. But, is this calculation valid for LES (pisoFoam)?
2- Is there any way to calculate “turbulence energy spectrum” of LES directly in openFoam ?
Thanks
sanysaly is offline   Reply With Quote

Old   November 13, 2013, 04:55
Default
  #2
New Member
 
Giulio S
Join Date: Oct 2013
Location: Italy
Posts: 4
Rep Power: 13
GiulioS is on a distinguished road
Quote:
Originally Posted by sanysaly View Post
Hi,
I am doing LES with pisoFoam. My questions that may be useful as post-processing tools and/or as a utility for validation of model are:
1- How can we calculate the Total Reynolds Stress? Based on thread (http://www.cfd-online.com/Forums/ope...tml#post342243),
We just need to “UPrime2Mean + RMean” (respectively resolved + SGS parts) to get the full stresses. But, is this calculation valid for LES (pisoFoam)?
2- Is there any way to calculate “turbulence energy spectrum” of LES directly in openFoam ?
Thanks
Dear sanysaly
The pisoFoam solver gives you the UPrime2Mean,referred to the "filtered scale", just like sad in the thread mentioned, so you have to add the contribution from the "SGS scale", just like:
(2.0/3.0)*I)*k_ - nuSGS_*twoSymm(fvc::grad(U_) ,
if you want to have the full Reynolds stress tensor.
For the second question, I suggest to calculate in an external software, just like twice the Fourier transform of the autocovariance.
Giulio S
Bernhard, PonchO and SHUBHAM9595 like this.
GiulioS is offline   Reply With Quote

Old   January 24, 2015, 16:28
Default Total Reynolds Stress in LES
  #3
Member
 
Join Date: Feb 2014
Posts: 63
Rep Power: 12
Uyan is on a distinguished road
Hi GiulioS,

This is an old post but i see you have suggested to calculate total Reynolds stress by considering
total Reynolds Stress = UPrime2Mean + Subgrid_ReynoldsStress.

But, my question is in the LES tutorial channel395, openFoam calculates reynolds stress only using UPrime2Mean, so which is correct?


postChannel utility.
Code:
     volScalarField Rxy(UPrime2Mean.component(symmTensor::XY));


     makeGraph(y, RxyValues, "uv", path, gFormat);

So which method is correct? I saw Eugene De Villiers also suggested your method. But I am confused now.

Thank you.
Uyan is offline   Reply With Quote

Old   January 8, 2017, 03:04
Default
  #4
Member
 
Mirage
Join Date: Jul 2012
Posts: 43
Rep Power: 14
Mirage is on a distinguished road
Hi there,

Did get an answer to your question?

Is it possible to use UPrime2Mean for the calculation of the energy spectrum ?

Thanks in advance

Quote:
Originally Posted by Uyan View Post
Hi GiulioS,

This is an old post but i see you have suggested to calculate total Reynolds stress by considering
total Reynolds Stress = UPrime2Mean + Subgrid_ReynoldsStress.

But, my question is in the LES tutorial channel395, openFoam calculates reynolds stress only using UPrime2Mean, so which is correct?


postChannel utility.
Code:
     volScalarField Rxy(UPrime2Mean.component(symmTensor::XY));


     makeGraph(y, RxyValues, "uv", path, gFormat);
So which method is correct? I saw Eugene De Villiers also suggested your method. But I am confused now.

Thank you.
Mirage is offline   Reply With Quote

Old   April 29, 2017, 08:40
Default
  #5
Member
 
Join Date: Feb 2014
Posts: 63
Rep Power: 12
Uyan is on a distinguished road
Hi Mirage,

I figured out that for a well resolved LES the modelled part of Reynolds stress is of very little magnitude.
So if you look at this paper, it's clear why only the resolved part is used.

LARGE EDDY SIMULATION OF TURBULENT
CHANNEL FLOWS
C.Fureby, A.D.Gosman, G.Tabor, H.G.Weller,

I assume you meant "turbulent energy spectrum" , i have not done that.
I think it's a good idea to record velocity signals on some points and follow the approach suggested by GiulioS.
Uyan is offline   Reply With Quote

Reply

Thread Tools Search this Thread
Search this Thread:

Advanced Search
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are On
Refbacks are On


Similar Threads
Thread Thread Starter Forum Replies Last Post
New implemented algebraic Reynolds stress model volker OpenFOAM 13 October 21, 2013 01:01
Question about shifting turbulence model from K-Omega to SSG Reynolds stress Anna Tian Main CFD Forum 2 January 20, 2013 13:36
Discussion: Reason of Turbulence!! Wen Long Main CFD Forum 3 May 15, 2009 10:52
Problem initializing Reynolds stress turbulence Vinicius Siemens 0 January 29, 2009 07:03
Turbulence: Reynolds stress equations kharicha FLUENT 0 March 16, 2006 09:50


All times are GMT -4. The time now is 19:12.