chimney fins

[@mikesteffen3378]

Also why car antennas (when cars still had antennas) sometimes have helical winding on them. Also why people wrap a bungee cord around their round car rooftop racks. It’s because the frequency of those vortices are audible and annoying.

[@emmajacobs5575]

I knew about the antenna thing, but had never heard of bungee cord around a round roofrack. Thanks!

[@brianrice7656]

I work with light poles which sometimes have issues related to vortex shedding. I don't think it's entirely accurate to say "the frequency of the oscillation is dependent on the speed of the air." Like a pendulum, the pole has a natural harmonic frequency depending on its height and stiffness and so on. The air speed will affect the amplitude of oscillation and how fast those vortexes can travel to neighboring poles/chimneys, but the frequency will be the same. A dangerous resonance can happen when 1. the wind direction lines up with 2 or more poles/chimneys and 2. the wind speed is relatively constant. I'd be curious to see the exact mechanism for how these fins disrupt vortex shedding explained! Maybe we could use them.

[@donnymurray7439]

Think it’s a funnel or stack