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

explicit residual smoothing working with multigrid method

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

Reply
 
LinkBack Thread Tools Search this Thread Display Modes
Old   August 30, 2010, 13:20
Smile explicit residual smoothing working with multigrid method
  #1
New Member
 
zhanglei
Join Date: Aug 2010
Posts: 1
Rep Power: 0
zhanglei is on a distinguished road
hi everyone, I'm working on a program solving the external inviscid flow around an airfoil. I am using unstructured mesh,Jameson cell-centered scheme,non-reflect far field boundary condition as well as local time step & explict residual smoothing. I'm using these schemes to solve the flow around naca0012 airfoil under an external flow speed ranging from subsonic to supersonic and they work well. later for optimizing purpose I tried to use multigrid method with these schemes.Right after that the program diverge quickly and I find that whenever I turn off the explicit residual smoothing option the whole progam converge again. without this option I can only use a CFL number up to around 1 to guarantee the convergence of the program( with a CFL of 1 the program will converge after 1500 iterations when the fixed acuracy is reached,without multigrid and with the same CFL number the program will converge after 15000 or even more iterations). It just seems that the explicit residual smoothing method doesn't work with multigrid, which is likely to be wrong since I have read some papers concerning these methods using together. when used in runge-kutta steps, the residual should add forcing function and become a "modified residual". Which of the residual and the "modified residual" is the one I ought to smooth? If anybody has solved the problem I met, what's the biggest CFL number you could use?
zhanglei is offline   Reply With Quote

Reply

Tags
multigrid

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
lift and drag on ship superstructures vaina74 OpenFOAM Running, Solving & CFD 3 June 8, 2010 13:30
MRFSimpleFOAM goes divergenced! renyun0511 OpenFOAM Running, Solving & CFD 0 November 19, 2009 03:11
reactingFoam: adiabatic flame temperature rFkhemek OpenFOAM 2 July 31, 2009 07:42
SimpleFoam k and epsilon bounded nedved OpenFOAM Running, Solving & CFD 1 November 25, 2008 21:21
MRFSimpleFoam amp cyclic patches david OpenFOAM Running, Solving & CFD 36 October 21, 2008 22:55


All times are GMT -4. The time now is 06:28.