I was wondering about something I observed yesterday. To give some background, one of my hobbies is slacklining. This is essentially like tight-rope walking but with a one inch piece of (in this case polyester) webbing. Usually the set-up is you have an anchor around a tree, a pulley system, the webbing, then another anchor around a second tree. Thus a 'static' end and a non-static end. You tension the line to an appropriate amount and the goal is to walk from one end to the other, working on balance and what not.
Anyways, yesterday there was a little bit of wind and when I stood on top of the webbing, the line, that was initially just barely whipping in the wind, started to oscillate up and down, and as I continued to stand on the line, the amplitude seemed to build on itself and get to be larger and larger oscillations. Once I got off the line it came back to just being in the air.
My question is this, what is going on and what is the best way to model this motion? Is it some kind of driven oscillatory motion? I'm not bouncing up and down, just standing on top. Do the waves travel through the line, into the tree and back building on itself?
How accurate of an analysis is possible? What method should be used? Statics, Dynamics, Lagrangian? Any input would be very welcome.