A mystery of fluid physics first noticed by da Vinci has puzzled scientists for centuries, and we now have an answer.
More than 500 years ago, Leonardo da Vinci was watching air bubbles float up through water — as you do when you're a Renaissance-era polymath — when he noticed that some bubbles inexplicably started spiraling or zigzagging instead of making a straight ascent to the surface.
For centuries, nobody has offered a satisfying explanation for this weird periodic deviation in the motion of some bubbles through water, which
has been called "Leonardo's paradox."
Now, a pair of scientists think they may have finally solved the longstanding riddle by developing new simulations that match high-precision measurements of the effect, according to
a study published on Tuesday in
Proceedings of the National Academy of Sciences.The results suggest that bubbles can reach a critical radius that pushes them into new and unstable paths due to interactions between the flow of water around them and the subtle deformations of their shapes. "The motion of bubbles in water plays a central role for a wide range of natural phenomena, from the chemical industry to the environment," said authors Miguel Herrada and Jens Eggers, who are fluid physics researchers at the University of Seville and the University of Bristol respectively, in the study. "The buoyant rise of a single bubble serves as a much-studied paradigm, both experimentally and theoretically."
"Yet, in spite of these efforts, and in spite of the ready availability of enormous computing power, it has not been possible to reconcile experiments with numerical simulations of the full hydrodynamic equations for a deformable air bubble in water," the team continued. "This is true in particular for the intriguing observation, made already by Leonardo da Vinci, that sufficiently large air bubbles perform a periodic motion, instead of rising along a straight line."
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Indeed, bubbles are so ubiquitous in our daily lives that it can be easy to forget that they are dynamically complicated and often tricky to experimentally study. Rising air bubbles in water are influenced by a host of intersecting forces — such as fluid viscosity, surface friction, and any surrounding contaminants — that contort the shapes of the bubbles and shift the dynamics of the water flowing around them.
What da Vinci noted, and other scientists have since confirmed, is that air bubbles with a spherical radius that is much smaller than a millimeter tend to follow a straightforward upward path through water, whereas larger bubbles develop a wobble that results in periodic spiral or zigzag trajectories.
Herrada and Eggers used the Navier-Stokes equations, which are a mathematical framework for describing the motion of viscous fluids, to simulate the complex interplay between the air bubbles and their watery medium. The team were able to pinpoint the spherical radius that triggers this tilt — 0.926 millimeters, which is about the size of a pencil tip — and describe the possible mechanism behind the squiggly motion.
A bubble that has exceeded the critical radius becomes more unstable, producing a tilt that changes the curvature of the bubble. The shift in curvature increases the velocity of water around the surface of the bubble, which kicks off the wobble motion. The bubble then returns to its original position due to the pressure imbalance created by the deformations in its curved shape, and repeats the process on a periodic cycle.
In addition to resolving a 500-year-old paradox, the new study could shed light on a host of other questions about the mercurial behavior of bubbles, and other objects that defy easy categorization. "While it was previously believed that the bubble's wake becomes unstable, we now demonstrate a new mechanism, based on the interplay between flow and bubble deformation," Herrada and Eggers concluded in the study. "This opens the door to the study of small contaminations, present in most practical settings, which emulate a particle somewhere in between a solid and a gas."
Reader Comments
A bubble that has exceeded the critical radius becomes more unstable, producing a tilt that changes the curvature of the bubble. The shift in curvature increases the velocity of water around the surface of the bubble, which kicks off the wobble motion. The bubble then returns to its original position due to the pressure imbalance created by the deformations in its curved shape, and repeats the process on a periodic cycle.
Are planets a bubble floating in a matrix of dark matter? Of which we really don't know what dark matter is. We have no concept of the reality at this time, is it a gravitational matrix, that binds the universe together. How could the universe be suspended in time and place? In a dark matter matrix, without some glue, so speak to hold it all together, could this be gravity, the unknown etheral substance that binds all of reality
This made me think of the Earths wobble, and the earth wobble related to processional cycles predicated by many ancient cultures in the world periodic time of around 25,000 years in earth times.
Some interesting articles
[Link] Why Does Earth's Axis of Rotation Wobble?
[Link] Mars is also a wobbly planet like Earth, and we don’t know why
And also this from the archive of NASA
[Link] the topics below
(7) Precession
"The Dawning of the Age of Aquarius"
The Precession of the Earth's Axis
Ice Ages
Some say the world will end in fire,
Some say in ice.
From what I've tasted of desire
I hold with those who favor fire.
But if it had to perish twice,
I think I know enough of hate
To say that for destruction ice
Is also great
And would suffice
The Milankovich Theory
Just sharing the pondering of my mind by reading this article.
“We are ignorant about X phenomena.”
“That phenomena is explained by this complimented theory and long-words.”
“Oh yes! I am no longer ignorant about that phenomena - I can now hide my ignorance behind those long complicated scientific words!”
Has this article actually reduced the amount of ignorance in the world? or has it just filled the world with more wordiness and jargon?