Relaxation factor

sunilpatil · April 16, 2013, 05:43

Hello sir,
In my transient analysis i am applying solar heat flux to the wall which varies from 0 to 24 [hr],heat flux is maximum at 12 PM.while solving solution goes smoothly up to 6 AM after that i am getting error floating point exception i think this is probably due to sudden variation in input heat flux at 6 AM my question is

i want to apply under-relaxation factor at this stage how to do this in CFX

Thank you sir
Sunil Patil

JuPa · April 16, 2013, 10:37

Floating point exception usually occurs when the solver wants to divide by zero.

Try double precision.

ghorrocks · April 16, 2013, 19:29

Fiddling with under relaxation factors is almost certainly NOT the solution. Forget about SIMPLE based solvers where you were constantly fiddling with them, CFX is very different to that.

But this question is an FAQ: http://www.cfd-online.com/Wiki/Ansys...do_about_it.3F

April 16, 2013, 05:43	Relaxation factor	#1
sunilpatil Senior Member sunil Join Date: Jul 2012 Location: Bangalore Posts: 179 Rep Power: 13	Hello sir, In my transient analysis i am applying solar heat flux to the wall which varies from 0 to 24 [hr],heat flux is maximum at 12 PM.while solving solution goes smoothly up to 6 AM after that i am getting error floating point exception i think this is probably due to sudden variation in input heat flux at 6 AM my question is i want to apply under-relaxation factor at this stage how to do this in CFX Thank you sir Sunil Patil

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April 16, 2013, 10:37		#2
JuPa Senior Member Mr CFD Join Date: Jun 2012 Location: Britain Posts: 361 Rep Power: 14	Floating point exception usually occurs when the solver wants to divide by zero. Try double precision.

April 16, 2013, 19:29		#3
ghorrocks Super Moderator Glenn Horrocks Join Date: Mar 2009 Location: Sydney, Australia Posts: 17,703 Rep Power: 143	Fiddling with under relaxation factors is almost certainly NOT the solution. Forget about SIMPLE based solvers where you were constantly fiddling with them, CFX is very different to that. But this question is an FAQ: http://www.cfd-online.com/Wiki/Ansys...do_about_it.3F