{"version": "1.0", "type": "rich", "title": "When I was a child, my father would take me trout fishing, and I spent hours marveling from the riverbank at the trouts\u2019 ability...", "author_name": "kontextmaschine", "author_url": "https://kontextmaschine.com", "provider_name": "kontextmaschine", "provider_url": "https://kontextmaschine.com", "url": "https://kontextmaschine.com/post/176243486473/", "html": "

ohdeargodwhy:

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fuckyeahfluiddynamics:

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When I was a child, my father would take me trout fishing, and I spent hours marveling from the riverbank at the trouts\u2019 ability to, seemingly effortlessly, hold their position in the fast-moving water. As it turns out, those trout really were swimming effortlessly, in a manner demonstrated above. The fish you see here swimming behind the obstacle is dead. There\u2019s nothing powering it, except the energy its flexible body can extract from the flow around it.\u00a0

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The obstacle sheds a wake of alternating vortices into the flow, and when the fish is properly positioned in that wake, the vortices themselves flex the fish\u2019s body such that its head and its tail point in different directions. Under just the right conditions, there\u2019s actually a resonance between the vortices and the fish\u2019s body that generates enough thrust to overcome the fish\u2019s drag. This means the fish can actually swim upstream without expending any energy of its own! The researchers came across this entirely by accident, and one of the questions that remains is how the trout is able to sense its surroundings well enough to intentionally take advantage of the effect. (Image and research credit: D. Beal et al.; via PhysicsBuzz; submitted by Kam-Yung Soh)

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Oh my god what the fuck

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