CFD Online Logo CFD Online URL
Home > Forums > Main CFD Forum

Oscillating airfoils: system identification

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

LinkBack Thread Tools Display Modes
Old   May 5, 2008, 19:45
Default Oscillating airfoils: system identification
Posts: n/a
Hi guys, I'm working on a simple aeroelastic system and have a 2 degree of freedom system (pitch & plunge) in unsteady flow. The technique is working well but I'm having problems in analysing the oscillations.

The code takes a long time to run and outputs the loads & pitch and plunge displacements. I can tell by eye whether these are growing (flutter) but am having problems getting a system identification algorithm to work.

I'm currently trying Prony's method as the results should, ideally, be able to be modelled as the sum of complex exponentials (i.e. the sum of damped cosine/sine signals). Unfortunately the efficacy of this approach varies depending on which airfoil/flow parameters I use. Sometimes my approximations are very good - sometimes they're not even close. There doesn't seem to be any way of knowing beforehand whether the Prony method is likely to produce good results. I should mention that my oscillation plots are smooth (no noise so Prony should be ok).

Could someone please suggest a simple method of system identification that I use for my model? If you could point me to a reference or two I'd be a happy bunny ) Iain
  Reply With Quote


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
CFX11 + Fortran compiler ? Mohan CFX 20 March 30, 2011 18:56
Transonic Aeroelastic CFD for Oscillating Airfoils Nicholas Amuyedo CFX 0 August 6, 2007 06:57
free code about "system identification" ztdep Main CFD Forum 1 April 14, 2007 20:58
System identification in simulation Luis Main CFD Forum 6 July 25, 2006 21:26
what is "system identification" ztdep Main CFD Forum 2 July 20, 2006 11:48

All times are GMT -4. The time now is 13:26.