However, those undulations eventually did cause one of the suspension cables to snap, creating an imbalance. The now-lopsided bridge began to twist along its center axis, as well as undulate, emitting a shrieking metallic wail in the process. It was this new movement that proved to be its undoing. The real culprit was something called aerodynamically induced self-excitation, or “flutter.” It’s a self-sustaining vibrational feedback loop, in essence.

While forced resonance is best exemplified by an opera singer shattering a wine glass with her voice, Motherboard’s Alex Pasternack likened flutter to an amp that shrieks whenever it gets too close to the microphone. (For anyone interested in all the gory engineering details, Pasternack’s lengthy examination is a must-read.) That kind of feedback can be cool when used in moderation by rock musicians, but let the feedback build up too much, and eventually you’ll blow out your speakers.

That’s essentially what happened to the Tacoma Narrows Bridge: Each time the bridge twisted along its center axis, it increased the effect of the wind instead of dampening it, with ever-larger vortices shedding off its edges. The feedback kept building and building in energy, until ultimately Galloping Gertie twisted itself apart.

This doesn’t detract from the Korean scientists’ paper’s main takeaway: that you can eliminate vortex shedding and significantly reduce drag by employing a twisty, helical shape when designing an object.


The daffodil’s unusual geometry isn’t especially well-suited for bridge design, and hence would not have saved Galloping Gertie. But better understanding of those aerodynamic forces will lead to better bridge designs in the future. And co-author Haecheon Choi said he and his colleagues already have a patent for a daffodil-inspired golf club. Similar principles could also be applied to things like antennae, lampposts, chimneys, and skyscrapers—all of which could benefit from better aerodynamical design.

[Physics of Fluids]