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

LRR and cyclic conditions

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

Reply
 
LinkBack Thread Tools Display Modes
Old   July 30, 2007, 11:21
Default For starters, this is not easy
  #1
Senior Member
 
Hrvoje Jasak
Join Date: Mar 2009
Location: London, England
Posts: 1,761
Rep Power: 21
hjasak will become famous soon enough
For starters, this is not easy - RSTM models are notoriously tricky to run with cyclics. Your problem will be worse if the geometry is only one cells thick, due to some issues of boosting the off-digaonal rather than matrix diagonal in cyclics. In any case, you will need to play around with the numerics and under-relaxation until you get it to work; once it starts up properly, all will be well.

I remember a bug in cyclics for tensors a long long time ago, but that has been eliminated in about 1999 - hopefully it dodn't come back...

Hrv
__________________
Hrvoje Jasak
Providing commercial FOAM/OpenFOAM and CFD Consulting: http://wikki.co.uk
hjasak is offline   Reply With Quote

Old   July 30, 2007, 15:37
Default Well, my geometry is in fact o
  #2
Member
 
Matthias Kern
Join Date: Mar 2009
Location: Karlsruhe, Germany
Posts: 36
Rep Power: 8
make is on a distinguished road
Well, my geometry is in fact only one cell thick.
I also had a lot of trouble using CFX with that grid but finally it converged applying local timescaling, which dampens a lot. Of course I don't have this choice in OpenFOAM. Nevertheless the quality of the grid is high considering a 6 grid.
So far I played around with under-relaxation and TVD schemes (Upwind was not beneficial), sadly without success.
Don't you have a hint for example which solver and scheme is most stable for the Reynolds stresses or which relation and range of epsilon and R relaxation is reasonable. I would be very happy about any help on that.
make is offline   Reply With Quote

Old   August 1, 2007, 11:41
Default I found the problem. Neither
  #3
Member
 
Matthias Kern
Join Date: Mar 2009
Location: Karlsruhe, Germany
Posts: 36
Rep Power: 8
make is on a distinguished road
I found the problem.
Neither the geometry nor the numerical setup caused my problems, its the system.

I'm working on a beowulf cluster consisting of SuSE 9.3 systems based on a 2.6.11.4 kernel.
My home system is SuSE 10.2 based on a 2.6.18.2 kernel. The OpenFOAM installation is identical using gcc-4.1.2. On my home system LRR converges without problems, but on our cluster even with the start solution taken from my home system the simulations crashes after the first iteration.
make is offline   Reply With Quote

Old   August 5, 2014, 09:47
Default
  #4
New Member
 
Jens
Join Date: Apr 2014
Posts: 26
Rep Power: 3
jensi_t is on a distinguished road
Hi,

i know that this thread is some years old but for me it seems to be up to date. I can run a dbnsTurbFoam-case with cyclic boundaries and LRR turbulence modeling on my local machine (Suse 13.1) both in serial and in parallel mode, but when I shift the same case to a Centos 6.3 cluster there is a huge increase in Rzz on one cyclic patch and the computation stops after a few timesteps.
Did someone solve that problem?

Thanks in advance!

Jens
jensi_t is offline   Reply With Quote

Old   August 13, 2014, 11:19
Default
  #5
New Member
 
Jens
Join Date: Apr 2014
Posts: 26
Rep Power: 3
jensi_t is on a distinguished road
Hi,

I solved the problem by using cyclicGgi boundaries and making them globalFaceZones. Calculation takes longer but at least it works.
I think in my case the problem occurs when the cyclics are split by decomposePar.
Anyway i'm still interested in a more elegant solution.

Jens
jensi_t is offline   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
Cyclic Boundary conditions johndeas OpenFOAM Running, Solving & CFD 1 January 4, 2008 21:34
Cyclic boundary conditions hadi OpenFOAM Running, Solving & CFD 0 June 29, 2007 10:46
periodic and cyclic boundary conditions Hadi Main CFD Forum 2 June 29, 2007 07:19
cyclic conditions Laurent FERRY CD-adapco 0 January 6, 2006 16:11
cyclic boundary conditions.. Zerrin CD-adapco 0 June 11, 2005 13:49


All times are GMT -4. The time now is 05:29.