Overflow Error Because of defining a New Coordinate Frame

ashtonJ · April 22, 2012, 23:26

Dear All,

I got "Floating point exception: Overflow" error, I have read all the post about this problem. My problem is because of defining a new coordinate frame.

I defined a Poiseuille velocity profile as inlet boundary condition of my model but the original coordinate frame is not in middle of the inlet surface, so my velocity is not zero at the centre, it is zero somewhere close to the edge of the inlet. To resolve this problem, I defined a new coordinate frame on the inlet surface and used the new coordinate frame for defining the inlet boundary condition. The problem is solved and I got the zero in the centre, however, in the first iteration of run, I got the "Floating point exception: Overflow" error.

Does anybody know where the problem originates from.

Kind regards,
AshtonJ

ghorrocks · April 23, 2012, 01:26

I have just written an FAQ on floating point error because it comes up so much:
http://www.cfd-online.com/Wiki/Ansys...do_about_it.3F

But you comment that in this case it appears the problem is due to local coordinate system. Have you tried to define the velocity profile without the local coord? Sure the maths is a bit more tricky but I think you are right when you say it is probably where the problem lies.

ashtonJ · April 23, 2012, 01:44

Thanks so much. Without a local coordinate frame, I don't get a symmetric poiseulle flow profile, the zero velocity is not in the middle of the inlet, it is near the edge.

ghorrocks · April 23, 2012, 08:08

The coordinate frame is a simple transformation. You just include the transformation in your CEL expression then you do not need the local coordinate system. The end result is identical.

And if your problem is due to some problem with local coordinate frames this will work around it.

April 22, 2012, 23:26	Overflow Error Because of defining a New Coordinate Frame	#1
ashtonJ Senior Member Ashkan Javadzadegan Join Date: Sep 2010 Posts: 255 Rep Power: 16	Dear All, I got "Floating point exception: Overflow" error, I have read all the post about this problem. My problem is because of defining a new coordinate frame. I defined a Poiseuille velocity profile as inlet boundary condition of my model but the original coordinate frame is not in middle of the inlet surface, so my velocity is not zero at the centre, it is zero somewhere close to the edge of the inlet. To resolve this problem, I defined a new coordinate frame on the inlet surface and used the new coordinate frame for defining the inlet boundary condition. The problem is solved and I got the zero in the centre, however, in the first iteration of run, I got the "Floating point exception: Overflow" error. Does anybody know where the problem originates from. Kind regards, AshtonJ

Similar Threads
Thread	Thread Starter	Forum	Replies	Last Post
UDF for defining a body force in Singel ROtating Reference Frame	teymourj	Fluent UDF and Scheme Programming	9	August 18, 2016 15:33
CFD Post- coordinate frame issue	GSbert	ANSYS	1	June 15, 2012 01:26
Moving coordinate frame	Roland R	CFX	3	November 28, 2011 09:59
coordinate frame	Jackie	CFX	2	March 6, 2003 00:22
Cylindrical coordinate frame	New User	CFX	3	August 10, 2002 06:41

April 23, 2012, 01:26		#2
ghorrocks Super Moderator Glenn Horrocks Join Date: Mar 2009 Location: Sydney, Australia Posts: 17,703 Rep Power: 143	I have just written an FAQ on floating point error because it comes up so much: http://www.cfd-online.com/Wiki/Ansys...do_about_it.3F But you comment that in this case it appears the problem is due to local coordinate system. Have you tried to define the velocity profile without the local coord? Sure the maths is a bit more tricky but I think you are right when you say it is probably where the problem lies.

April 23, 2012, 01:44		#3
ashtonJ Senior Member Ashkan Javadzadegan Join Date: Sep 2010 Posts: 255 Rep Power: 16	Thanks so much. Without a local coordinate frame, I don't get a symmetric poiseulle flow profile, the zero velocity is not in the middle of the inlet, it is near the edge.

April 23, 2012, 08:08		#4
ghorrocks Super Moderator Glenn Horrocks Join Date: Mar 2009 Location: Sydney, Australia Posts: 17,703 Rep Power: 143	The coordinate frame is a simple transformation. You just include the transformation in your CEL expression then you do not need the local coordinate system. The end result is identical. And if your problem is due to some problem with local coordinate frames this will work around it.