# divergence detected in AMG solver

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 July 26, 2006, 02:02 divergence detected in AMG solver #1 selvaganesh Guest   Posts: n/a i am calculating turbulent viscosity which includes damping function using UDF. when i hook this udf and when iterating it gives "deivergence detected in AMG solver in x momentum. how can i solve my problem plz somebody help me

 January 31, 2014, 22:53 #2 New Member   Join Date: Sep 2013 Posts: 4 Rep Power: 12 I have same problem but after 3 second the divergence in AMG solver happens. please help me(I reduced URF of my UDF but it didnt worked.

 January 31, 2014, 23:04 #3 Member   le hoang anh Join Date: Oct 2012 Posts: 96 Rep Power: 13 Check your mesh which is allway the cause

February 5, 2014, 03:20
#4
New Member

Nick Prendergast
Join Date: Dec 2013
Posts: 28
Rep Power: 12
Quote:
 Originally Posted by lehoanganh07 Check your mesh which is allway the cause
I would say incorrect boundary conditions can also cause divergence.

and as a another point, if you're using an explicit transient solver you need to ensure that c= (velocity*delta t)/delta x is less than or equal to 1 for stability, definitely affect convergence.

and this should help troubleshoot your model:
http://www.cfd-online.com/Wiki/Ansys..._inaccurate.3F

Nick

February 5, 2014, 03:49
#5
New Member

Nick Prendergast
Join Date: Dec 2013
Posts: 28
Rep Power: 12
Quote:
 Originally Posted by lehoanganh07 Check your mesh which is allway the cause
I would say incorrect boundary conditions can also cause divergence.

and as a another point, if you're using an explicit transient solver you need to ensure that c= (velocity*delta t)/delta x is less than or equal to 1 for stability, definitely affect convergence.

and this should help troubleshoot your model:
http://www.cfd-online.com/Wiki/Ansys..._inaccurate.3F

Nick

 February 5, 2014, 03:55 #6 New Member   Join Date: Jan 2014 Posts: 5 Rep Power: 12 during using solver at start reduce the under relaxation factor . it will solve your problem of divergence ..

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