CFD Online Logo CFD Online URL
www.cfd-online.com
[Sponsors]
Home > Forums > General Forums > Main CFD Forum

Is it feasible to apply implicit scheme in LES

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

Reply
 
LinkBack Thread Tools Search this Thread Display Modes
Old   September 3, 2008, 02:50
Default Is it feasible to apply implicit scheme in LES
  #1
EagleGao
Guest
 
Posts: n/a
Hi all, I'am trying to apply gmres implicit scheme to my LES code. But I found it converged slowly at each step in the case of Decaying Isotropic Turbulence(DIT) simulation. I used 7 points central difference scheme for spatial discretization. And a LU-SGS preconditioner was used for the gmres method. Does anyone have suggestion for the time integration scheme in LES ? It is not suitable to use implicit scheme in LES ? Thanks!
  Reply With Quote

Old   September 3, 2008, 11:18
Default Re: Is it feasible to apply implicit scheme in LES
  #2
Joe
Guest
 
Posts: n/a
I am not familiar with GMRES, but there is no fundamental reason that you can not use an implicit scheme. The issue is accuracy versus computational time. Your code has discretization errors due to your grid size and your time step size. For an implicit scheme, you can take very large time steps. This combined with the fact that implicit schemes are generally 1st or 2nd order means your error in the time discretization could be significant. So taking large time steps may not be a good thing. If this is the case you might as well use a faster explicit method and save on cpu time. The only way to check to see if this is the case is to do a time step study (similar to a grid study). Halve the time step and recompute. If the solution is unchanged, you are good.
  Reply With Quote

Old   October 24, 2011, 15:04
Default
  #3
New Member
 
C.Harish
Join Date: Jun 2011
Posts: 15
Rep Power: 14
harish_0689@ is on a distinguished road
Hey EagleGao, even i am trying to use implicit schemes for the euler equation and using the GMRES matrix solver. Even i found its converging slower than the explicit in terms of CPU time. And i was searching for the LU-SGS solver. Can u suggest me how and where can i get the LU-SGS solver? i am in a serious need of that.
harish_0689@ 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
CFX 11 Scheme for LES in Multiphase Man CFX 12 May 25, 2009 21:26
problem about numerical scheme in LES. libin Main CFD Forum 4 July 1, 2004 05:32
The numerical scheme in LES? Martin Main CFD Forum 1 May 24, 2004 05:49
the numerical scheme for LES. John S Main CFD Forum 2 March 14, 2004 08:52
Komogrov time scale and implicit scheme for LES Li Yang Main CFD Forum 1 January 17, 2004 02:13


All times are GMT -4. The time now is 16:45.