CFD Online Logo CFD Online URL
www.cfd-online.com
[Sponsors]
Home > Forums > Software User Forums > ANSYS > FLUENT

Oscillating residuals

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

Like Tree1Likes
  • 1 Post By vinerm

Reply
 
LinkBack Thread Tools Search this Thread Display Modes
Old   April 12, 2020, 16:22
Default Oscillating residuals
  #1
New Member
 
Muhammad Rizwan
Join Date: Mar 2020
Posts: 11
Rep Power: 2
rizwan4081 is on a distinguished road
I am trying to perform a ventilation analysis of a tunnel with a source of fire inside it. I used the k epsilon and k omega SST for turbulence. Can please someone tell me the reason for this issue?k omegaSST.jpg

k epsilon.jpg
rizwan4081 is offline   Reply With Quote

Old   April 13, 2020, 11:32
Default Residuals
  #2
Senior Member
 
vinerm's Avatar
 
Vinerm
Join Date: Jun 2009
Location: Nederland
Posts: 2,948
Blog Entries: 1
Rep Power: 31
vinerm will become famous soon enough
The residuals are not oscillating. You are running a transient case and the residuals are supposed to drop from rather high values to low values within each time-step. That's what you are observing.
RaiderDoctor likes this.
__________________
Regards,
Vinerm

PM to be used if and only if you do not want something to be shared publicly. PM is considered to be of the least priority.
vinerm is offline   Reply With Quote

Old   April 14, 2020, 08:43
Default
  #3
New Member
 
Muhammad Rizwan
Join Date: Mar 2020
Posts: 11
Rep Power: 2
rizwan4081 is on a distinguished road
Understood. For a transient simulation I get peaks and troughs as it reaches convergence. But sometimes the trend of the oscillations are increasing in amplitude. And how can one judge the solution and say that the solution is converged?
rizwan4081 is offline   Reply With Quote

Old   April 14, 2020, 09:16
Default Monitors
  #4
Senior Member
 
vinerm's Avatar
 
Vinerm
Join Date: Jun 2009
Location: Nederland
Posts: 2,948
Blog Entries: 1
Rep Power: 31
vinerm will become famous soon enough
Set up a few monitor points, such as, pressure, velocity, temperature, etc., at some boundaries. These should either achieve a constant value or a periodic oscillation in the value.
__________________
Regards,
Vinerm

PM to be used if and only if you do not want something to be shared publicly. PM is considered to be of the least priority.
vinerm is offline   Reply With Quote

Reply

Tags
residuals

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
Oscillating residuals in steady flow problem Mohit Singh Main CFD Forum 3 February 23, 2016 15:39
Reason for oscillating residuals fayaazhussain Main CFD Forum 3 August 21, 2014 11:31
Oscillating residuals and no convergence! Sherlock_1812 OpenFOAM Running, Solving & CFD 7 August 20, 2014 10:39
Solution not converging, but oscillating residuals around a constant value Irene FLUENT 2 February 7, 2012 12:55
Oscillating Residuals in Finer Mesh Case Jake FLUENT 3 June 16, 2005 10:34


All times are GMT -4. The time now is 22:44.