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-   -   over flow error (http://www.cfd-online.com/Forums/cfx/122974-over-flow-error.html)

behnam67 September 2, 2013 04:39

over flow error
 
hello everybody
I'm running a simulation about a anemometer in wind tunnel

On CFX - Solver I got this error:

ERROR #001100279 has occurred in subroutine ErrAction.

Floating point exception: Overflow

Do you know which could be my mistake?
total time=2
time step=0.002
inlet .. velocity=20 m/s
transient
please help me .... thanks

Lance September 2, 2013 04:48

http://www.cfd-online.com/Forums/cfx...ease-read.html
Include enough detail in your question.

Overflow:
http://www.cfd-online.com/Wiki/Ansys...do_about_it.3F


behnam67 September 2, 2013 15:11

1 Attachment(s)
thanks
this is my ccl

ghorrocks September 2, 2013 18:20

Have you read the post and FAQ linked to be Lance? It contains important information on this topic.

Why are you doing this as a rigid body simulation? What is moving? If you are using rigid body to model the anemometer then forget that and use rotating frames of reference instead.

Also, how did you set your time step? A guess? Or was there something objective to determine it.

behnam67 September 3, 2013 04:48

cup is moving.
how I can use rotating frames of reference?
can you explain?
my total time achived in experimental test.time step is guess.

ghorrocks September 3, 2013 19:06

Have a look at the tutorials on rotating machinery, such as a rotor/stator for how to set up these models.

A very common mistake for beginners to to use too large a time step. The easiest way to avoid this mistake is to use adaptive timestepping, homing in on 3-5 coeff loops per iteration. Make sure the max and min time step size are wide enough you never hit them. And set the max coeff loops to 10. Then at least your time step size will be about right.

behnam67 September 4, 2013 17:01

With default values of time step decrease factor and time step increase factor that are 0.8, 1.06 respectively, overflow occur in 350 iteration.
what values do you suggest for them?
thanks

ghorrocks September 4, 2013 17:47

The defaults are fine. If this does not converge then the problem is something else. Please post an image of what you are modelling and the output file from just before the crash.

behnam67 September 5, 2013 10:27

1 Attachment(s)
this is my cup anemometer

ghorrocks September 5, 2013 18:12

An image of your mesh and how you have implemented it would help.

Have you converted to rotating frames of reference yet?

behnam67 September 6, 2013 05:46

2 Attachment(s)
I dont know how to use rotating frames of reference.
can you explain,please?
thanks.
With a time step of 0.001 the simulation continues to 0.5 s(500 iteration),
then over flow error accur.
should I decrease my time step less than 0.001?

ghorrocks September 6, 2013 06:32

Please read my post #6 again. I have already answered your question on rotating frames of reference and already commented on your time step selection.


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