CFD Online Logo CFD Online URL
Home > Forums > FLUENT

Residuals Fluctuate after 3000 iter in inviscid

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

LinkBack Thread Tools Display Modes
Old   February 8, 2008, 13:56
Default Residuals Fluctuate after 3000 iter in inviscid
Posts: n/a
Hi all, I am running a problem of an aircraft on FLUENT 6.3. I am running inviscid model. The mesh size is i.7 Million. The problem is that for the first 3000 iterations the resiudals go smooth and then ALL(x, y, z velocitites energy) residuals start Fluctuating with very small amplitude. with 10 i peak per iteration I cant undersand wats the reason for that because solution is not going to converge even after 5000 itr. The problem was run on Parallel
  Reply With Quote

Old   February 8, 2008, 18:12
Default Re: Residuals Fluctuate after 3000 iter in invisci
Posts: n/a
Make sure your mesh quality is good and if so try relaxing the solution to dampen out the residuals.

  Reply With Quote

Old   February 13, 2008, 12:43
Default Re: Residuals Fluctuate after 3000 iter in invisci
Posts: n/a
Are you using a steady-sate model or a time dependent? If you're using a time dependent, the oscillations can be caused by numerical diffusion. The way to avoid these fluctuations consists in adaptin' time step in function of the general display of residuals. but if you're using a steady state model, I don't really know how to help you
  Reply With Quote

Old   October 12, 2011, 00:04
New Member
Join Date: Jun 2010
Posts: 15
Rep Power: 9
satyendra is on a distinguished road
hi maxime,

i am doing analysis of a furnace in fluent 6.3(geometry modeled in gambit 2.24). i have made structured mesh in most of the volume except at the corners of the mould.

initially when the hot gases' velocity were low it was converging, but i was not getting required temperature inside mould. hence i increased the flow rate without changing the model.

But now except energy, all other residuals i.e continuity, k, x, y, z velocity and epsilon are fluctuating. following are the specs:
1. unsteady flow.
2. turbulent k-epsilon and RNG model
3. time step = 1

satyendra 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
why residuals fluctuate? sagar CFX 6 October 11, 2011 17:33
Force can not converge colopolo CFX 13 October 4, 2011 22:03
Accuracy and convergence pawan1989 FLUENT 5 April 15, 2010 17:17
Convergence - scaled vs unscaled residuals HS FLUENT 1 November 7, 2005 06:45
Inviscid Drag at subsonic, subcritical Mach # Axel Rohde Main CFD Forum 1 November 19, 2001 13:19

All times are GMT -4. The time now is 23:48.