Wonder of ScienceOct 20, 2023

An owl gliding through a cloud of helium-filled soap bubbles reveals wingtip and tail vortices.

Video credit: Usherwood et al.
Source: https://journals.biologists.com/jeb/article/223/3/jeb214809/223686/High-aerodynamic-lift-from-the-tail-reduces-drag

High aerodynamic lift from the tail reduces drag in gliding raptors

Summary: Aerodynamic lift from gliding hawk and owl tails, revealed by tracking helium bubbles, is inconsistent with passive stability or minimizing induced drag, but indicates a role in reducing viscous drag.

The Company of Biologists
Show threadPeteOct 21, 2023

@wonderofscience

Vortices always come in pairs because the total curl in the fluid has to add up to zero.

Show threadSamuRaiDec 17, 2023
@pete @wonderofscience nieve question. Can they come in a triplet with two having half the curl and opposite of the third maintaining the zero sum?
Show threadPeteDec 17, 2023

@samurai @wonderofscience

Short answer: Maybe
Longer answer: I don’t know
Long answer: It’s complicated

Show threadSamuRai
@pete @wonderofscience as an economist, when I think about something “simple” like fluid dynamics, and how quickly it gets complicated, it amazes me that we know anything about economics at all.
Dec 18, 2023 at 7:15amWeb
Show threadPeteDec 18, 2023
@samurai @wonderofscience my fluids lecturer said he would go and watch jumbo jets taking off at the airport and exclaimed in a bemused but very posh public school accent that he didn’t “know how the bloody things got off the ground”
Show threadSamuRaiDec 18, 2023
@pete @wonderofscience as I couldn’t settle on a singular reply, I offer a Choose Your Own Adventure::
If you choose “My uncle was a pilot and he didn’t know either. Thankfully, he knew how they landed.” turn to page 57.
If you choose “That’s understandable when you assume a spherical plane.” turn to page 33.