To Predict Turbulence, Just Count the Puffs (2014) | Hacker News Reader

To Predict Turbulence, Just Count the Puffs (2014)

nautil.us

58 pointsdnetesn8 comments

Turbulence seems to be very weird. This article talks about the birth and death rate of puffs. In a modified version of the Navier-Stokes equation Terrence Tao was able to construct logic gates and use those to create a self replicating eddy.

https://www.quantamagazine.org/20140224-a-fluid-new-path-in-...

> Turbulence seems to be very weird.

Right up there with "the Riemann hypothesis is quite difficult." (Of course, probably nothing beats the irony in naming of the Fundamental Lemma (https://en.wikipedia.org/wiki/Fundamental_lemma_%28Langlands...).)

I love nautilus because it can make the most seemingly inane things incredibly interesting. I've never thought about turbulence at all; or even guessed it would be difficult to figure out the cause but this, for lack of a better term, opened my eyes.

Feynman described turbulence as "the most important unsolved problem of classical physics."

Another quote, attributed both to Heisenberg and to Horace Lamb: "When I meet God, I am going to ask him two questions: Why relativity? And why turbulence? I really believe he will have an answer for the first."

And the very related problem of the existence and smoothness of solutions to the Navier-Stokes equations is one of the famous millennium problems.

Unless you have access to a DOE-grade supercomputer :) good interview here w/ one of the pioneers of Large Eddy Simulation for turbulence physics:

http://www.cascadetechnologies.com/pioneering-large-eddy-sim...

LES is an approximation, and there are cruder (RANS) and finer (DNS) ones available. And while these are very cool and useful e.g. for studying how turbulence affects other things (structures, particle in suspension etc.) they don't tell us much about turbulence itself.

I am always intrigued by the topic of turbulence and its implications in weather prediction. One of the key challenges of weather prediction is our inability to understand / predict atmospheric turbulence...most importantly 'chaotic turbulences'.

Details (European Research Council): http://erc.europa.eu/succes-stories/understanding-turbulence...

I love the examples of turbulence and laminar flow in Fantastic Mr Fox - hard to find on youtube but this clip[0] has about 3 seconds of what I'm talking about

[0] https://www.youtube.com/watch?v=7vjMc_HlNic @ 1:22-1:24

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