Mysteries of Turbulence Unraveled


#1

Interesting article from Scientific American Mysteries of Turbulence Unraveled.

Simulations follow how swirls in a fluid transfer and dissipate energy

“When I meet God, I’m going to ask him two questions: why relativity? And why turbulence? I really believe he’ll have an answer for the first.”

I never head of Andrey Kolmogorov until a couple years ago, lately he seems to turn up everywhere

This is from Wikipedia - Vortex Shedding
Vortex-street-animation
Vortex shedding behind a circular cylinder. In this animation, the flow on the two sides of the cylinder are shown in different colors, to show that the vortices from the two sides alternate. Courtesy, Cesareo de La Rosa Siqueira.


Vortex shedding as winds pass Heard Island ( bottom left ) in the southern Indian Ocean resulted in this Kármán vortex street in the clouds


#2

“Big whirls have little whirls,
That feed on their velocity;
And little whirls have lesser whirls,
And so on to viscosity.”

― [Lewis Fry Richardson]

Couldn’t resist :grinning:

Cheers,

Earl


#3

Not much difference between the linked article in the OP and Lewis Fry Richardson:

Their results validate a theory formulated by Russian mathematical physicist Andrei Kolmogorov in the early 1940s. Among its consequences is that turbulence occurs in a cascade: large eddies break down into smaller ones, which in turn split into even smaller ones, in a fractal fashion.


#4

Does this mean that turbulence can be thought of as a kind of pseudo-viscosity?

Huh. I guess the Bubbles in Dartmouth behave completely differently from the bubbles in St. John’s.


#5

I studied turbulence behind ships with great interest 50 years ago at two ship model testing tanks but also aboard ships. Turbulence develops when the laminar boundary layer between ship hull and the sea water breaks up into eddies due to friction, dynamic effects, etc. 50 years later nobody seems to have clarified the matter.
Anyway, a clean, smooth hull reduces turbulence and reduces resistance and fuel consumption and increases speed.