CFD Online Logo CFD Online URL
www.cfd-online.com
[Sponsors]
Home > Forums > Software User Forums > OpenFOAM > OpenFOAM Running, Solving & CFD

about Subgrid-scale model

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

Reply
 
LinkBack Thread Tools Search this Thread Display Modes
Old   September 8, 2010, 12:57
Default about Subgrid-scale model
  #1
Member
 
Kim Yusik
Join Date: Dec 2009
Posts: 39
Rep Power: 16
impecca is on a distinguished road
Hi, foamers.

Is there anyone who can recommend me a SGS model for the airfoil case?
(of course LES, Reynolds number is less than 100,000)
Based on some literature reviews, some works are done with 'Dynamic smagorinsky' model and some works are done with 'Mixed-sclae model' ( Sagaut, P. 1996 : Numerical simulations of separated flows with subgrid models) or 'Mixed-time model' (Inagaki et al. 2005 : A Mixed-time-scale SGS model with fixed model - parameters for practical LES).


I've checked 'dynamic Smagorinsky model' in openfoam but one line (below) is ambiguous in the dynSmagorinsky.C file.


00060 dimensionedScalar MMMM = average(magSqr(MM));


here I don't understand what 'average' means. Does it mean averaging in whole domain? if it means averaging whole domain, this model doesn't seem so attractive since original model averaged only in homogeneous directions.

So I tried to look for 'Mixed-scale model' or 'Mixed-time model' in openfoam but these two models are not implemented yet. I am also wondering is there anyone who implemented these two models into openfoam.


To sum,
which sgs model do you recommend for the airfoil case ?
what is the 'average' mean in the 'dynamic Smagorinsky model' ?
Is there anyone who implement 'Mixed -scale model' or 'Mixed-time model' into the openfoam ?

Thanks in advance

Yusik
impecca is offline   Reply With Quote

Old   September 9, 2010, 11:26
Default
  #2
Senior Member
 
Alberto Passalacqua
Join Date: Mar 2009
Location: Ames, Iowa, United States
Posts: 1,912
Rep Power: 36
alberto will become famous soon enoughalberto will become famous soon enough
Quote:
Originally Posted by impecca View Post
I've checked 'dynamic Smagorinsky model' in openfoam but one line (below) is ambiguous in the dynSmagorinsky.C file.


00060 dimensionedScalar MMMM = average(magSqr(MM));


here I don't understand what 'average' means. Does it mean averaging in whole domain? if it means averaging whole domain, this model doesn't seem so attractive since original model averaged only in homogeneous directions.
The homogeneous direction does not exist in general cases. As a consequence who implemented the model decided to average on the domain. You can easily replace the average with a local average, as done by many authors in the literature. It means changing only a few lines of the code.

Similarly, the mixed-time model simply redefines the SGS viscosity as a function of a certain time-scale, with some theoretical advantage. You could implement it by starting from an existing model (like the dynamic one) in OF.

Best,
__________________
Alberto Passalacqua

GeekoCFD - A free distribution based on openSUSE 64 bit with CFD tools, including OpenFOAM. Available as in both physical and virtual formats (current status: http://albertopassalacqua.com/?p=1541)
OpenQBMM - An open-source implementation of quadrature-based moment methods.

To obtain more accurate answers, please specify the version of OpenFOAM you are using.
alberto is offline   Reply With Quote

Old   September 12, 2010, 14:47
Default
  #3
Member
 
Kim Yusik
Join Date: Dec 2009
Posts: 39
Rep Power: 16
impecca is on a distinguished road
wrong questions sorry

Last edited by impecca; September 14, 2010 at 07:33. Reason: wrong questions
impecca is offline   Reply With Quote

Old   December 20, 2013, 07:54
Default
  #4
Senior Member
 
Jian Zhong
Join Date: Feb 2012
Location: Birmingham
Posts: 109
Rep Power: 14
zxj160 is on a distinguished road
Quote:
Originally Posted by alberto View Post

Similarly, the mixed-time model simply redefines the SGS viscosity as a function of a certain time-scale, with some theoretical advantage. You could implement it by starting from an existing model (like the dynamic one) in OF.

Best,
Hi Alberto,
Could you suggest a related tutorial case? I am tring to using the dynamic Smagorinsky model, but without success.

My best regards,
Jian
zxj160 is offline   Reply With Quote

Old   December 20, 2013, 11:36
Default
  #5
Senior Member
 
Jian Zhong
Join Date: Feb 2012
Location: Birmingham
Posts: 109
Rep Power: 14
zxj160 is on a distinguished road
Quote:
Originally Posted by alberto View Post

Similarly, the mixed-time model simply redefines the SGS viscosity as a function of a certain time-scale, with some theoretical advantage. You could implement it by starting from an existing model (like the dynamic one) in OF.

Best,
Hi Alberto,
Could you suggest a related tutorial case? I am tring to using the dynamic Smagorinsky model, but without success.

My best regards,
Jian
zxj160 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
Use of k-epsilon and k-omega Models Jade M Main CFD Forum 40 January 27, 2023 08:18
Problem on EDC model for coal combustion lei FLUENT 4 September 3, 2015 10:39
simulation results for k-w model and SST model Li CFX 7 June 29, 2007 05:19
LES subgrid model John Deas FLUENT 1 June 18, 2007 14:32


All times are GMT -4. The time now is 02:56.