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

k-epsilon source term

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

Reply
 
LinkBack Thread Tools Display Modes
Old   May 13, 2005, 08:13
Default k-epsilon source term
  #1
max
Guest
 
Posts: n/a
Hi everybody I am working with k-epsilon model (density-variable version) to compute a simple jet in still air. My problem is that the convergence rate of the iterative solver of the linear system (Coniugate Gradient Method Stabilized) is very poor. I have already tried to improve it using a lower under-relaxation factor and/or CFL number but I have no improvements. I suppose the kind of the source term linearization for k and epsilon is not the best one. In particular the dilatation term is the one which destroy convergence rate. Have you some references where I can find some source term linearizations and/or critical discussion about them? Thanks MAX
  Reply With Quote

Old   May 19, 2005, 13:53
Default Re: k-epsilon source term
  #2
tejus
Guest
 
Posts: n/a
USe tri diagnol matrix analysis (TDMA) to get your equations converge.it really workes. you can get the detail from the text book " Intoduction to finite difference methods" by Veerstag and Malashekara.
  Reply With Quote

Old   May 20, 2005, 02:27
Default Re: k-epsilon source term
  #3
max
Guest
 
Posts: n/a
I am sorry, but I can not find this book. Can you check exactly the title and authors? I have another question: does this method work also for unstructure grids? I guess you can apply it only for structured problems. Nevertheless I will have look to your book, once I find it. Thanks
  Reply With Quote

Old   May 20, 2005, 04:01
Default Re: k-epsilon source term
  #4
zxaar
Guest
 
Posts: n/a
i have been running k-e model on unstrcutred grids based on bicgstab and yes i also feel that convergence is very slow. for the same mesh fluent converges very fast, even though i make coarsening level to 0, (i am not sure whether fluent is using multigrids in that option too), but if i assume fluent uses gauss siedel only (when i make coarsening to zero), it is quite surprising that fluent solution conerges so fast. i will only come to know if i implement multigrids into my solver and this will take some time.

i am not sure what other people have experience with k-e using other solvers , for example FOAM (i guess) can work with biCGstab.
  Reply With Quote

Reply

Thread Tools
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 On
Pingbacks are On
Refbacks are On


Similar Threads
Thread Thread Starter Forum Replies Last Post
swak4foam building problem GGerber OpenFOAM Installation 54 April 24, 2015 16:02
momentum source term zwdi FLUENT 13 December 5, 2013 18:58
DxFoam reader update hjasak OpenFOAM Post-Processing 69 April 24, 2008 01:24
DecomposePar links against liblamso0 with OpenMPI jens_klostermann OpenFOAM Bugs 11 June 28, 2007 17:51
UDFs for Scalar Eqn - Fluid/Solid HT Greg Perkins FLUENT 0 October 13, 2000 23:03


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