CFD Online Logo CFD Online URL
Home > Forums > Software User Forums > ANSYS > FLUENT


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

LinkBack Thread Tools Display Modes
Old   March 7, 2005, 21:28
Default Divergence
Posts: n/a

When I try to iterate, thsi msg appears

"Error: divergence detected in AMG solver: pressure correction Error Object: ()"

Does anyone know what it means and how can I overcome this?

  Reply With Quote

Old   March 8, 2005, 03:54
Default Re: Divergence
Melaku Habte
Posts: n/a

This error is usually related to the pressure correction factor ( under-relaxation factor). What causes it? Well many reasons: do u have any UDF, what is your model? transient/steady state? compressible/or not? especially if you have a floating operating pressure its very likely to happen. It can also come from your mesh size. So not much to say without knowing your particular model. But to have a short/general answer to it you can try to reduce the pressure under-relaxation factor from the menue - solve - controls - solution and reduce under-relaxation factor for pressure to a value roughly 0.2 - 0.3 or may be lower if it is during the initial period and then keep on increasing as the solution progresses. The default value is 0.3 but you can try to reduce and see if it helps. This is the most basic stuff to do. As I said there are many other reasons for it to happen. Fluent makes the pressure correction based on that factor. The higher the factor the bigger the change in pressure correction and the faster your solution converges IF EVERYTHING IS OK.


Melaku Habte.
  Reply With Quote

Old   March 8, 2005, 04:09
Default Re: Divergence
Posts: n/a
Try to use the coupled solver. Luca
  Reply With Quote

Old   March 8, 2005, 07:04
Default Re: Divergence
Posts: n/a

If you gonna change Under-relax, then consider the following: For the steady flow, the nearly optimem value for sum of under-relaxation of pressure and velocity is considered to be <=1.1( peric,pg205). But you can find optimum values for your case by changing these parametrs so that the sum equals to 1.1 (for one case i found it to be 0.6 and 0.4 for press and momentum). I am not sure about some guess of these values in unsteady case. May be somebody can help about that.

Good luck sawa
  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
UDF divergence of a vector cris FLUENT 3 September 4, 2014 18:06
Divergence problem for species transport model MY FLUENT 3 January 11, 2014 05:46
Quarter Burner mesh with periosic condition SamCanuck FLUENT 2 August 31, 2011 11:34
Role of divergence shekharc Main CFD Forum 7 July 5, 2005 12:08
divergence in MAC Method Maciej Matyka Main CFD Forum 2 December 19, 2000 11:43

All times are GMT -4. The time now is 19:32.