CFD Online Logo CFD Online URL
www.cfd-online.com
[Sponsors]
Home > Forums > CFX

over flow error

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

Like Tree1Likes
  • 1 Post By ghorrocks

Reply
 
LinkBack Thread Tools Display Modes
Old   September 2, 2013, 04:39
Default over flow error
  #1
New Member
 
hani
Join Date: Sep 2013
Posts: 7
Rep Power: 2
behnam67 is on a distinguished road
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
behnam67 is offline   Reply With Quote

Old   September 2, 2013, 04:48
Default
  #2
Senior Member
 
Lance
Join Date: Mar 2009
Posts: 472
Rep Power: 10
Lance is on a distinguished road
Before you post a question please read this
Include enough detail in your question.

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

Lance is offline   Reply With Quote

Old   September 2, 2013, 15:11
Default
  #3
New Member
 
hani
Join Date: Sep 2013
Posts: 7
Rep Power: 2
behnam67 is on a distinguished road
thanks
this is my ccl
Attached Files
File Type: zip setup.zip (3.2 KB, 1 views)
behnam67 is offline   Reply With Quote

Old   September 2, 2013, 18:20
Default
  #4
Super Moderator
 
Glenn Horrocks
Join Date: Mar 2009
Location: Sydney, Australia
Posts: 9,153
Rep Power: 73
ghorrocks has a spectacular aura aboutghorrocks has a spectacular aura aboutghorrocks has a spectacular aura about
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.
ghorrocks is offline   Reply With Quote

Old   September 3, 2013, 04:48
Default
  #5
New Member
 
hani
Join Date: Sep 2013
Posts: 7
Rep Power: 2
behnam67 is on a distinguished road
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.
behnam67 is offline   Reply With Quote

Old   September 3, 2013, 19:06
Default
  #6
Super Moderator
 
Glenn Horrocks
Join Date: Mar 2009
Location: Sydney, Australia
Posts: 9,153
Rep Power: 73
ghorrocks has a spectacular aura aboutghorrocks has a spectacular aura aboutghorrocks has a spectacular aura about
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.
hmasenger likes this.
ghorrocks is offline   Reply With Quote

Old   September 4, 2013, 17:01
Default
  #7
New Member
 
hani
Join Date: Sep 2013
Posts: 7
Rep Power: 2
behnam67 is on a distinguished road
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
behnam67 is offline   Reply With Quote

Old   September 4, 2013, 17:47
Default
  #8
Super Moderator
 
Glenn Horrocks
Join Date: Mar 2009
Location: Sydney, Australia
Posts: 9,153
Rep Power: 73
ghorrocks has a spectacular aura aboutghorrocks has a spectacular aura aboutghorrocks has a spectacular aura about
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.
ghorrocks is offline   Reply With Quote

Old   September 5, 2013, 10:27
Default
  #9
New Member
 
hani
Join Date: Sep 2013
Posts: 7
Rep Power: 2
behnam67 is on a distinguished road
this is my cup anemometer
Attached Images
File Type: jpg 2.jpg (65.0 KB, 3 views)
behnam67 is offline   Reply With Quote

Old   September 5, 2013, 18:12
Default
  #10
Super Moderator
 
Glenn Horrocks
Join Date: Mar 2009
Location: Sydney, Australia
Posts: 9,153
Rep Power: 73
ghorrocks has a spectacular aura aboutghorrocks has a spectacular aura aboutghorrocks has a spectacular aura about
An image of your mesh and how you have implemented it would help.

Have you converted to rotating frames of reference yet?
ghorrocks is offline   Reply With Quote

Old   September 6, 2013, 05:46
Default
  #11
New Member
 
hani
Join Date: Sep 2013
Posts: 7
Rep Power: 2
behnam67 is on a distinguished road
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?
Attached Images
File Type: png preview.png (41.3 KB, 2 views)
File Type: png preview1.png (44.5 KB, 2 views)
behnam67 is offline   Reply With Quote

Old   September 6, 2013, 06:32
Default
  #12
Super Moderator
 
Glenn Horrocks
Join Date: Mar 2009
Location: Sydney, Australia
Posts: 9,153
Rep Power: 73
ghorrocks has a spectacular aura aboutghorrocks has a spectacular aura aboutghorrocks has a spectacular aura about
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.
ghorrocks is offline   Reply With Quote

Reply

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
Native ParaView Reader Bugs tj22 OpenFOAM Paraview & paraFoam 263 November 24, 2013 10:55
Compile problem ivanyao OpenFOAM Running, Solving & CFD 1 October 12, 2012 09:31
Building OpenFOAM1.7.0 from source ata OpenFOAM Installation 42 May 14, 2012 20:48
Saving ParaFoam views and case sail OpenFOAM Paraview & paraFoam 9 November 25, 2011 15:46
Compiling problems with hello worldC fw407 OpenFOAM Installation 21 January 6, 2008 17:38


All times are GMT -4. The time now is 13:38.