Von Kármán vortex eddy streets - we spent like a month studying those horrible things in fluid dynamics class.
Imagine you are standing on a crowded sidewalk, facing thousands of people walking towards you. The people represent air or water. Theoretically, you'd only have people bump into the front of you. In real life, you also get jostled from side to side.
As crowds of people (and fluid flow) is never perfectly uniform, someone's elbow bumps against your right side, shoving you to your left. That moves you enough that you bump into someone on your left side, which shoves you to your right. If the people are walking towards you at just the wrong speed, you'll be bounced back and forth uncontrollably.
If you are a flagpole, bridge, or a smokestack, this is a bad thing, as you'll vibrate yourself to pieces. Much of fluid dynamics class was spent learning how to PREVENT this behaviour (i.e. adding strakes) rather than causing it.
If you have something moving back and forth a short distance at a fairly constant frequency, there are several ways that you can extract power. A crankshaft can turn it into rotary motion (efficient, but mechanical parts are expensive and prone to wear), or you can use piezoelectric materials to directly create electricity (inefficient, but cheap and low maintenance).
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Imagine you are standing on a crowded sidewalk, facing thousands of people walking towards you. The people represent air or water. Theoretically, you'd only have people bump into the front of you. In real life, you also get jostled from side to side.
As crowds of people (and fluid flow) is never perfectly uniform, someone's elbow bumps against your right side, shoving you to your left. That moves you enough that you bump into someone on your left side, which shoves you to your right. If the people are walking towards you at just the wrong speed, you'll be bounced back and forth uncontrollably.
If you are a flagpole, bridge, or a smokestack, this is a bad thing, as you'll vibrate yourself to pieces. Much of fluid dynamics class was spent learning how to PREVENT this behaviour (i.e. adding strakes) rather than causing it.
If you have something moving back and forth a short distance at a fairly constant frequency, there are several ways that you can extract power. A crankshaft can turn it into rotary motion (efficient, but mechanical parts are expensive and prone to wear), or you can use piezoelectric materials to directly create electricity (inefficient, but cheap and low maintenance).
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Sidebar note: James Hudson would have had to know fluid dynamics in order to build his signature power-suit, right?
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