This short film from photographer Roman De Giuli focuses on ethereal and abstract fluids. What you’re watching is primarily paint, with a little in the way of flow additives. There’s lovely marbling and some impressively sharp edges, but mostly you can just sit back and enjoy the flow! (Image and video credit: R. De Giuli)
Enormous whirlpools are not simply the work of overactive imaginations. There are several spots in the world, including Japan’s Naruto Strait, that regularly see these spectacular vortices.
Naruto’s whirlpools are formed through the interaction of tidal currents with the local topography. Spring tides funneled through the vee-shaped strait can reach speeds of 20 kph as they rush between the Pacific Ocean and the Inland Sea. Below the surface, there’s also a deep depression that helps bring the tides together in such a way that it generates vortices 20 meters in diameter.
In normal times, the whirlpools are a significant tourist attraction during the springtime. Travelers can view them from tour boats, helicopters, and from the Onaruto Bridge. (Image credits: whirlpools – Mainichi/N. Yamada, Discover Tokushima; artwork: Hiroshige; via Mainichi; submitted by Alan M.)
Hydrogen is a promising alternative to carbon-based fuels, but it comes with its own special challenges. Hydrogen gas is extremely flammable, including under circumstances that would normally quench flames, as shown in this recent study.
What you see above are water condensation patterns left behind after the passage of hydrogen flames through a narrow gap between two glass plates. With other fuels, the narrow confinement and low fuel ratio used in these experiments would keep the flames from spreading. But because hydrogen is so light, it diffuses much faster than other fuels, allowing it to spread in these fractal patterns despite its confinement. Engineers will have to account for hydrogen’s easy spread when designing containment strategies. (Image and research credit: F. Veiga-López et al.; via APS Physics)
We’re all familiar with the problem of pouring a liquid from a narrow-necked bottle. To a certain extent, tilting the bottle further will reduce the time it takes to empty, but if you tilt too far, your smooth pour becomes violent glugging as bubbles forming at the bottle’s mouth block liquid from exiting.
Researchers find that the time it takes to empty a bottle depends both on the qualities of the liquid — its viscosity and surface tension — and on the geometry of the bottle. In particular, they found that the shape of the bottle influences how quickly bubbles grow at the bottle’s mouth when tilted to the critical angle. Their findings suggest that higher tilt angles and faster pours can be achieved by optimizing bottle geometry. (Image and research credit: L. Rohilla and A. Das; via phys.org)
NASA Goddard has produced another gorgeous visualization of how various aerosols move around our world. This visualization is constructed from data collected between August 2019 and January 2020, which means that it captures numerous typhoons as well as the extreme bushfires that occurred in Australia.
Different colors represent different aerosol sources: carbon (red), sulfate (green), dust (orange), sea salt (blue), and nitrate (pink). The brighter the color, the higher the concentration of aerosols. With this, we see steady patterns of natural sea salt transport and the billowing flow of dust from Saharan Africa. But we can also see manmade pollution from sources across the Northern Hemisphere, as well as major output from the Australian bushfires. It’s a good reminder that none of us is truly isolated in this interconnected world of ours. (Video and image credit: NASA Goddard; via Flow Vis)
Eric Mesplé is an artist, but he’s also a blacksmith, welder, programmer, engineer, and innovator. Many of his sculptures feature ferrofluids, magnetic liquid whose movement is driven by electromagnets Mesplé designs and builds himself. In this video from Wired, we get a behind-the-scenes look at some of his work, and to me, one of the big takeaways is just how clearly science, engineering, and technology are married to art in Mesplé’s work. I imagine this is true of many of today’s artists! (Video credit: Wired)
I’ve covered some odd studies in my time, but this might be the strangest: to understand how active polymers affect viscosity, researchers loaded drunk worms into a rheometer. Active polymers are long-chain molecules that, like worms, can move on their own using stored energy or by extracting energy from their surroundings. Their dynamics are tough to study, though, because individual polymers are almost impossible to observe while a suspension of them is being deformed.
Enter the humble sludge worm. Often sold as fish food, these worms — like the polymers they’re meant to imitate — are individually quite wiggly but, given their size, are far easier to observe. Researchers placed them in a custom rheometer in a solution of water and observed how the worm mass responded when sheared by a spinning top plate (Image 3). Like active polymers, the worms exhibited shear-thinning; the faster the plate spun, the lower the worms’ viscosity, likely because the additional force helps align the worms.
But how do active worms compare with passive ones? The obvious solution would be to repeat their tests with dead worms, but the researchers found a more humane method: by adding some alcohol to the water, they temporarily reduced the worms’ activity, allowing them to compare active and passive worms (Image 2). Once rinsed in water, the worms sobered up and returned to their normal activity levels.
The researchers found that both the active and passive worms exhibited shear-thinning as the force on them increased, but the shear-thinning in the active worms was not as pronounced, presumably because the movements of individual worms prevented them from aligning smoothly. (Image and research credit: A. Deblais et al.; via Gizmodo and APS Physics)
This false-color satellite image — the recent winner of NASA Earth Observatory’s Tournament Earth 2020 — shows sands and seaweed off the coast of the Bahamas. Ocean currents and tides eroded these elaborate fluted designs in much the same way that winds sculpt desert dunes. The overlap in form is no accident; as seen in recent work, researchers are finding that both air and water move granular materials like sand according to the same rules. (Image credit: S. Andrefouet; via NASA Earth Observatory)
Eutectic gallium-indium alloy is a room-temperature liquid metal with an extremely high surface tension. Normally, that high surface tension would keep it from spreading easily. But once the metal oxidizes, the surface tension drops. When that oxidation is combined with an electric field, the metal spreads into fingers. The higher the voltage, the more complex the fingering patterns. (Image and video credit: K. Hillaire et al.)
A bioluminescent phytoplankton bloom is causing a stir among California beachgoers. During the daytime, aggregations of Lingulodinium polyedra appear reddish-brown in color (think the classic ‘red tide’). But at night the phytoplankton bioluminesce, specifically when they’re disturbed by a change in shear force. This is why the brightest glows are visible in crashing waves or around the boards of surfers.
Beautiful as it appears, blooms like these are deadly to marine life. The excess numbers of phytoplankton strip water of oxygen, causing mass die-offs among fish. Even residents several miles inland of the beaches are reporting the unpleasant smell that results. (Image credits: AP; video credit: Scripps Institute of Oceanography; via Gizmodo)
