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Bren November 20, 2007 13:40

Vibrating system analysis - a good introduction?
Hi Guys, I'm writing a code at the moment that will determine the vibrations of a simple 2d airfoil. The airfoil has 2 degrees of freedom, pitch and plunge and the code determines the time history of pitch and plunge degrees of freedom. The code is working and produces plots of plunge & pitch displacements.

I'm trying to determine the velocity at which flutter occurs. Basically what I want is some method that will detect whether the oscillations are growing or shrinking with time so I can determine whether my results correspond to stable or unstable flows. I have been given an old NASA report on the complex-sine curve fitting technique (Desmarais) but to a newbie like me it's about as much use as an electric abacus. I've also read that the method has since been replaced with much faster and more efficient methods. For the problem I'm solving I'm not interested in the efficiency of the algorithm - one that is robust would be preferable. The desmarais paper doesn't really cover the method in sufficient detail for me to code it up myself.

Could someone please suggest a useful introductory text on the subject of system identification? Failing that if someone knows of a relatively simple algorithm that might help I'd be very grateful.

Many thanks, Bren

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