The Juno mission has been revealing angles of Jupiter we’ve never seen before. This photo shows Jupiter’s northern temperate latitudes and NN-LRS-1, a.k.a. the Little Red Spot (lower left), the third largest anticyclone on Jupiter. The Little Red Spot is a storm roughly the size of the Earth and was first observed in 1993. As an anticyclone, it has large-scale rotation around a core of high pressure and rotates in a clockwise direction since it is in the northern hemisphere. Jupiter’s anticyclones seem to be powered by merging with other storms; in 1998, the Little Red Spot merged with three other storms that had existed for decades. (Image credit: NASA/JPL-Caltech/SwRI/MSSS/Gerald Eichstaedt/John Rogers; via Bad Astronomy)
Search results for: “art”
Freezing Bubbles
Soap bubbles are wonderfully ephemeral, their surfaces constantly in motion as air currents, surface tension variations, and temperature differences make them dance. In this video, though, photographer Paweł Załuska focuses on freezing soap bubbles. Watching the growth of ice crystals across the bubbles’ thin surface is mesmerizing. Snowflake-like crystals can nucleate anywhere on the film and, as in the sequence at 0:48, those crystals can float around on the bubble’s surface like snowflakes drifting on a breeze until enough of the film solidifies to bring the bubble to a halt and, then, a collapse. (Video credit: P. Załuska/ZALUSKart; via Gizmodo)
Accidental Painting
Some paintings of Mexican artist David Alfaro Siqueiros feature patchy, spotted areas of contrasting color formed by what Siqueiros described as “accidental painting”. Many modern artists use this technique as well. By pouring thin layers of two different colors atop one other, Siqueiros was able to generate seemingly spontaneous patterns like those shown above. In fact, what Siqueiros was using was a density-driven fluid instability! These patterns will only appear when a denser paint is poured atop a lighter one. They’re the result of a Rayleigh-Taylor instability – the same behavior that makes beautiful swirls of cream in coffee and the finger-like protrusions seen in supernovae.
Although a density difference is necessary to generate accidental painting, other factors like the paint layer’s thickness and viscosity affect the final pattern. For those who are mathematically-inclined, this paper has a linear stability analysis that shows how density difference, viscosity, and other factors affect the cell sizes in the pattern. (Image and research credits: S. Zetina et al.; GIF source)
As the Dust Blows In
This towering cloud of dust is known as a haboob, and while it appears apocalyptic, it is a relatively common occurrence in parts of the world, including the U.S. southwest and the Middle East. Haboobs often form when a collapsing thunderstorm releases a downburst of cold air. That wind picks up loose dust along the ground and creates a wall of sediment that may be as much as 100 kilometers wide and several kilometers tall. Inside the haboob, winds can reach speeds as high as 100 kph and visibility can be reduced to nearly zero. Because of this, the storms can be quite dangerous, especially to anyone who attempts to drive during one. (Image credit: D. Bryant)
Wrapping Up
It’s often at the intersection of topics that we can learn something new and fascinating. The latest video from The Lutetium Project shows examples of this at the intersection of solid mechanics and fluid dynamics with a look at elastocapillarity. Breaking that word down, that’s where elasticity – that stretchy quality associated with solids – meets capillarity – the surface-tension-dominated behavior of a fluid. In particular, they explore some of the mind-boggling and surprising interactions that happen between drops, bubbles, and thin flexible fibers smaller than the width of a human hair. Check out the full video below. (Images credit: K. Dalnoki-Veress et al.; video credit: The Lutetium Project)
Vibrated to Bits
Sound and vibration can be powerful tools for controlling liquids. In this animation, a water/glycerin drop violently bursts into a cloud of droplets when it is vibrated vertically 1000 times per second by a piezoelectric actuator. This vibration shakes the drop with accelerations of 150 g. Initially, the amplitude is small enough to simply create ripples around the drop’s circumference. As it increases, the drop deforms more at the edges and starts to eject droplets there. When the vibration hits a critical amplitude, the entire drop explodes into droplets. The technique is called vibration-induced droplet bursting, and its near-instantaneous ability to atomize drops makes it a candidate for applications like spray cooling microprocessors or spray coating a solid surface. (Video credit: B. Vukasinovic, source)
Dissolving
It looks like the fiery edge of a star’s corona, but this photo actually shows a dissolving droplet. The droplet, shown as the lower dark region in this shadowgraph image, is a mixture of pentanol and decanol sitting in a bath of water. Pentanol is a type of alcohol that is fully miscible with decanol and is water soluble, so that it will dissolve into the surrounding water over time. Decanol, on the other hand, is immiscible with water, so that part of the droplet won’t mix with the surrounding water.
The bright swirls along the droplet’s edge show areas with more pentanol. As the alcohol dissolves into the water, it forms a buoyant plume at the top of the droplet that rises due to pentanol’s lower density. That rising plume draws fresh water in from the sides, shown by the upper white arrows. Inside the droplet, flow moves in the opposite direction, from the top toward the outer edges. This is a result of uneven surface tension within the droplet. Scientists are interested in understanding the dynamics of these multiple component drops for applications like printing, where it’s desirable for pigments in an ink drop to be distributed evenly as the drop dries. (Image credit: E. Dietrich et al.)
Turbine Wakes in the Sea
What we we build always has an impact on the environment around us. The white dots you see in the image above are an array of offshore wind turbines, standing in waters 20 to 25 meters deep. The brownish lines extending from each turbine show the underwater wakes of the turbines, colored by the sediment they’ve picked up. As with trees in a snowstorm, the currents flowing past the base of the turbine likely form a horseshoe vortex that lifts up the sediment into the wake. Because the tides in this area reverse direction every six hours, these sediment plumes can appear quite dynamic in satellite imagery, frequently changing strength and direction. (Image credit: NASA Earth Observatory)
A Water Balloon on a Bed of Nails
If you dropped a water balloon on a bed of nails, you’d expect it to burst spectacularly. And you’d be right – some of the time. Under the right conditions, though, you’d see what a high-speed camera caught in the animation above: a pancake-shaped bounce with nary a leak. Physically, this is a scaled-up version of what happens to a water droplet when it hits a superhydrophobic surface.
Water repellent superhydrophobic surfaces are covered in microscale roughness, much like a bed of tiny nails. When the balloon (or droplet) hits, it deforms into the gaps between posts. In the case of the water balloon, its rubbery exterior pulls back against that deformation. (For the droplet, the same effect is provided by surface tension.) That tension pulls the deformed parts of the balloon back up, causing the whole balloon to rebound off the nails in a pancake-like shape. For more, check out this video on the student balloon project or the original water droplet research. (Image credits: T. Hecksher et al., Y. Liu et al.; via The New York Times; submitted by Justin B.)
Shot Through a Drop
Shoot a sphere through a drop with sufficient speed, and you’ll see something like the composite photo above. Going from right to left, the projectile is initially coated in liquid and stretches the fluid behind it as it continues flying. This forms a thin sheet of fluid called a lamella with a thicker, uneven rim at its far end. The lamella continues stretching until the projectile breaks through and detaches. Now the lamella starts rebounding back on itself as surface tension struggles to keep the fluid together. A new rim forms on the front, and both the front and back rims thicken as the lamella collapses. Along the rims thicker portions start forming droplets – like spikes on a crown – as the surface-tension-driven Plateau-Rayleigh instability starts breaking the structure down. The untenable sheet of fluid will break up into a cloud of smaller, satellite droplets when it can hold together no longer. (Image credit: V. Sechenyh et al., video)