Posted by Mike on April 11th, 2008 in material, power generation, vibrations, wind

http://www.rdmag.com/ShowPR.aspx?PUBCODE=014&ACCT=1400000100&ISSUE=080 4&RELTYPE=MIC&PRODCODE=0000000&PRODLETT=EI&CommonCount=0

A Zenit-3SL rocket explodes on its floating launch platform—an incident initally described as an “anomaly”—on January 30th. (credit: Sea Launch)

I came across this interesting piece of research about sound and vibrations induced by sounds and while some folks would just blow by it without notice, I could not help but read this and start thinking about the Tacoma Narrows Bridge.

Almost everyone has seen videos of the galloping bridge that destroyed itself in a wind induced, harmonic frenzy. Again, “wind induced” because only the wind was at play in its demise, and “harmonic” because vibrations, then oscillations, then destruction happen because those vibrations added together to produce bigger vibrations, which are amplified into larger and larger oscillation to the point of the bridge tearing itself apart.

What is interesting is that this is just an example of how adding a little bit of energy to a system at just the right point can cause huge consequence. It is like pushing someone on a swing. All you have to do is push with just enough energy to overcome the friction -mechanical and air- in the system and then just a bit more on every push and pretty soon the swing and rider will go over the top. (Do this with someone you don’t like, not your kids, by the way.)

To the point of this: These folks at Georgia Tech found a way to simulate the sonic vibrations (an energy source) as they propagate through the system (of the rocket) accumulate and reinforce themselves to the point of destruction of the system. They were able to isolate the sonic induced, harmonic vibrations, visualize the accumulation and flow patterns and understand how they could cause mechanical failure.

This simulation, in and of itself, is fascinating - at least to me- and really reinforces the interplay between energy and matter; how it is generated and most importantly how it is transmitted, reinforced and absorbed. Think about how energy is transmitted, reinforced and absorbed in and through a solid - like the steel in a bridge, or a fluid, like rocket fuel or air, and you will begin to understand something beautiful, elegant and amazing, the interplay of matter and energy. Look for another article on phonons (right, go Google this) to help tie this vibration thing together. I owe this to you.