How fluids transform from order to disorder

Researchers may have identified a fundamental mechanism by which turbulence develops by smashing vortex rings head-on into each other, recording the results with ultra-high-resolution cameras, and reconstructing the collision dynamics using a 3D visualization program. The researchers have gained unprecedented insight into how fluidic systems transform from order to disorder.

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Tau.Neutrino said:

How fluids transform from order to disorder

Researchers may have identified a fundamental mechanism by which turbulence develops by smashing vortex rings head-on into each other, recording the results with ultra-high-resolution cameras, and reconstructing the collision dynamics using a 3D visualization program. The researchers have gained unprecedented insight into how fluidic systems transform from order to disorder.

more…

So nice, and unexpected, to see fundamental fluid mechanics in the news.

> the mechanics of that descent into chaos have puzzled scientists for centuries.

So true.

> Turbulence occurs when an ordered fluid flow breaks into small vortices, which interact with each other and break into even smaller vortices, which interact with each other and so-on, becoming the chaotic maelstrom of disorder

Known as the turbulence cascade, we’ve even plagiarised an Ogden Nash poem to describe it.

Bigger whirls have smaller whirls that feed on their vorticity.
And smaller whirls yet smaller whirls and so on to viscosity.

> determine the global flows in the ocean depends on how well we model turbulence

Yes, I say glumly.

Glumly because it’s known, there’s a mathematical proof, that it’s impossible to model turbulence well.

> At every length-scale, vortices are straining and compressing each other to generate a chaotic picture

Chaotic is the right word. This chaos is the origin of the butterfly effect.

> First, the rings stretch outward as they smash into each other and the edges form antisymmetric waves. The crests of these waves develop into finger-like filaments, which grow perpendicularly between the colliding cores.

That much is already known. The rest is new.

> the energy spectrum at the late-stage breakdown of the vortices follows the same tell-tale scaling of fully developed turbulence.

Good. It’s the time-dependence of this energy spectrum that is the interesting bit.

mollwollfumble said:

Known as the turbulence cascade, we’ve even plagiarised an Ogden Nash poem to describe it.

Bigger whirls have smaller whirls that feed on their vorticity.
And smaller whirls yet smaller whirls and so on to viscosity.

If Nash wrote that, he did something remarkable; it was published in 1872 (in A Budget of Paradoxes by Augustus De Morgan) whereas Nash was born in 1902. De Morgan parodied a portion of Jonathan Swift’s On Poetry: A Rhapsody. The “adaptation” you’ve quoted was written by Lewis F. Richardson in 1922.

btm said:

mollwollfumble said:

Known as the turbulence cascade, we’ve even plagiarised an Ogden Nash poem to describe it.

Bigger whirls have smaller whirls that feed on their vorticity.
And smaller whirls yet smaller whirls and so on to viscosity.

If Nash wrote that, he did something remarkable; it was published in 1872 (in A Budget of Paradoxes by Augustus De Morgan) whereas Nash was born in 1902. De Morgan parodied a portion of Jonathan Swift’s On Poetry: A Rhapsody. The “adaptation” you’ve quoted was written by Lewis F. Richardson in 1922.

Spike Milligan also parodied it.
Big fleas have smaller fleas on their backs to bite ‘em
The smaller fleas have yet smaller fleas and so on ad infinitum.

Tamb said:

btm said:

mollwollfumble said:

Known as the turbulence cascade, we’ve even plagiarised an Ogden Nash poem to describe it.

Bigger whirls have smaller whirls that feed on their vorticity.
And smaller whirls yet smaller whirls and so on to viscosity.

If Nash wrote that, he did something remarkable; it was published in 1872 (in A Budget of Paradoxes by Augustus De Morgan) whereas Nash was born in 1902. De Morgan parodied a portion of Jonathan Swift’s On Poetry: A Rhapsody. The “adaptation” you’ve quoted was written by Lewis F. Richardson in 1922.

Spike Milligan also parodied it.
Big fleas have smaller fleas on their backs to bite ‘em
The smaller fleas have yet smaller fleas and so on ad infinitum.

No, that was De Morgan. The full poem is:

Great fleas have little fleas
Upon their backs to bite ‘em;
Little fleas have lesser fleas,
And so ad infinitum.

The great fleas themselves in turn
Have greater fleas to go on;
While these again have greater still,
And greater still and so on.

btm said:

Tamb said:

btm said:

If Nash wrote that, he did something remarkable; it was published in 1872 (in A Budget of Paradoxes by Augustus De Morgan) whereas Nash was born in 1902. De Morgan parodied a portion of Jonathan Swift’s On Poetry: A Rhapsody. The “adaptation” you’ve quoted was written by Lewis F. Richardson in 1922.

Spike Milligan also parodied it.
Big fleas have smaller fleas on their backs to bite ‘em
The smaller fleas have yet smaller fleas and so on ad infinitum.

No, that was De Morgan. The full poem is:

Great fleas have little fleas
Upon their backs to bite ‘em;
Little fleas have lesser fleas,
And so ad infinitum.

The great fleas themselves in turn
Have greater fleas to go on;
While these again have greater still,
And greater still and so on.

Thanks. Although I did see Spike reciting it on TV.