CFD Online Logo CFD Online URL
Home > Forums > Main CFD Forum

What does low frequency oscillation phenomena tell in residuals

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

LinkBack Thread Tools Display Modes
Old   July 24, 2013, 04:10
Default What does low frequency oscillation phenomena tell in residuals
Join Date: Mar 2013
Posts: 40
Rep Power: 4
heksel8i is on a distinguished road

I was wondering what creates a low frequency oscillation in residuals like in the particular image as an attachment.

I would bet that it is due to a coarse mesh x-direction, because y-direction velocity is not oscillating so much and because turbulence quantities are no converging as quickly. I just have never seen such a low frequency phenomena, though beginner I am.
Attached Images
File Type: png low_osc.png (10.9 KB, 23 views)
heksel8i is offline   Reply With Quote

Old   July 24, 2013, 04:34
Senior Member
Filippo Maria Denaro
Join Date: Jul 2010
Posts: 1,775
Rep Power: 23
FMDenaro will become famous soon enough
If you think that the computational grid acts as a cut-off filtering and the numerical schemes smoothes high resolved frequencies, then it is quite common that the spectrum of the error will be dumped quickly at high frequancy and slowly at low frequencies.
In some way, this is at basis of the multigrid ideas, resolve the equations on wider grids to smooth more quick the low frequencies of the error.

In your case I suppose that the error is more "energetic" along x than along y
FMDenaro is offline   Reply With Quote

Old   July 24, 2013, 18:00
Senior Member
Martin Hegedus
Join Date: Feb 2011
Posts: 467
Rep Power: 9
Martin Hegedus is on a distinguished road
Looks like a separation bubble trying to converge.
Martin Hegedus is offline   Reply With Quote


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
The oscillation of scaled residuals is very big ZQWY FLUENT 0 February 16, 2012 22:00
extremely low residuals ranjith CFX 2 March 4, 2010 06:45
Oscillation of residuals in DPM (Ergent need!) yooceframandi FLUENT 1 February 28, 2006 07:46
Multicomponent fluid Andrea CFX 2 October 11, 2004 05:12
jet oscillation at low inlet Re wood Main CFD Forum 1 October 21, 1999 13:45

All times are GMT -4. The time now is 09:02.