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  • If you've ever flown on a plane,

  • odds are you're very familiar with turbulence

  • and it left you rathershaken.

  • But despite turbulence constantly showing up in our skies

  • or in whirlpools in our bathwater,

  • scientists don't have a mechanistic framework to describe

  • how vortexes drive cascades of energy that lead to turbulence.

  • So, to try and develop one, scientists at Harvard busted out a high speed camera,

  • some colorful dye, and—I can't believe I get to say thisvortex cannons!

  • Two of them fit in a 75-gallon aquarium, where they fired plumes of liquid through water.

  • The cannons were pointed squarely at each other so that the vortexes could meet in a head-on collision.

  • Thanks to a little fluorescent dye, the scientists could then watch how the two vortex rings

  • interacted when they met.

  • Watching the results looks like the most over-engineered lava lamp you could ever imagine,

  • but I promise you there's science happening.

  • To capture the interactions of the two vortexes clearly, the researchers used a high speed camera.

  • That let them see everything clearly and smoothly in slow motion,

  • but only in two dimensions on the x- and y-axes.

  • To get a three dimensional view of the interactions,

  • they synched the camera with a pulsing laser that scanned the z-plane of the collision.

  • That way for each frame from the high speed camera,

  • there would also be a laser scan cutting through the place where the vortexes collided.

  • With the high speed 3D models of the collision recorded,

  • they could observe in detail what exactly was going on.

  • They noticed that the rings stretched outward when they hit each other,

  • and that antisymmetric waves formed at the edge of their expansion.

  • The edges of those waves developed filaments that grew perpendicularly towards the opposite vortex.

  • Neighboring filaments counter rotated and created smaller vortexes.

  • When those vortexes interacted, they also formed filaments, repeating the cycle.

  • The researchers observed three generations of an orderly cascading cycle

  • before everything broke down into turbulence.

  • They think this could point to a universal mechanism of how energy cascades down until it dissipates,

  • regardless of scale.

  • This work has applications beyond making cool posters to put in a black-lit room.

  • Modeling turbulence can help us predict weather patterns,

  • map the flows in the oceans,

  • or understand how an airliner can fly with eddies trailing behind it.

  • And having a model for turbulence could also be useful as average global temperatures rise,

  • because severe turbulence is expected to double, or even triple, by 2050.

  • Yeah, climate change is going to make air travel even bumpier.

  • But this research is just a step towards that broader understanding.

  • At the scale that jolts airplanes and makes you cling to the poor sap in the middle seat,

  • things are a lot more complex than this experiment.

  • Still, for a brief time at the late stages of the lab-made vortex collision,

  • the experiment seems to have created the same conditions as real-life turbulence.

  • So, more research is needed.

  • I just hope scientists stop before they create supervillain level vortex cannons.

  • Does turbulence worry you, or are you a smooth customer when the going gets rough?

  • Let us know in the comments.

  • High speed cameras can pull off some really neat tricks, like seeing around corners.

  • Maren has more on that here.

  • Make sure to subscribe to Seeker and thanks for watching.

If you've ever flown on a plane,

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渦流碰撞可能會揭開秩序如何轉為無序的序幕。 (Vortex Collisions Could Unravel How Order Turns to Disorder)

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    Summer 發佈於 2021 年 01 月 14 日
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