Built from approximately 90,000 individual images, “Fusion of Helios” reveals the wisp-like corona of our Sun. Astrophotographers Andrew McCarthy and Jason Guenzel joined forces to combine eclipse images with data from NASA to build this fusion of art and science. Jets of plasma, known as spicules, dot the sun’s surface, and a towering tornado of plasma shoots off one side. For scale, that vortex stretches as far as 14 Earths stacked atop one another. (Image credit: A. McCarthy and J. Guenzel; via Colossal)
When bubbles burst, they release smaller droplets from the jet that rebounds upward. Depending on their size, these droplets can fall back down or get lofted upward on air currents that spread them far and wide. Thus, knowing what kind of bubbles produce small, fast droplets is important for understanding air pollution, climate, and even disease transmission.
The jet from a bubble of clean water is broad and slow, releasing fewer and larger drops.
In a recent study, researchers compared droplets made by clean, water-only bubbles, and the ones generated from water bubbles with a thin layer of oil coating them. The clean bubbles created jets that were broad and relatively slow moving; this motion produced a few large drops that quickly fell back down.
The jet from an oil-covered bubble is skinny and fast-moving. It produces many small droplets.
In contrast, the oil-slicked bubbles made a narrow, fast-moving jet that broke into many small droplets. These droplets could stay aloft for longer periods, indicating that contaminated water can produce more aerosols than clean. (Image credit: top – J. Graj, bursting – Z. Yang et al.; research credit: Z. Yang et al.; submitted by Jie F.)
Acoustic cameras use arrays of microphones to isolate where sounds are coming from. As Steve Mould shows in this video, they have some incredibly cool properties. They can show engineers which part of a device is producing particular sound frequencies, which is handy, for example, when trying to quiet a vacuum cleaner or learn which wheels on a train need maintenance. They can also show how sound moves around a room; near the end of the video, you can see the echo from a clap flashing around a room. Check out the full video for more! (Video credit: S. Mould)
Droplets with particles in them can leave complex stains when they dry — just look at coffee rings and whiskey marks! Here, researchers look at the patterns left on glass by small droplets that evaporated and left behind their nanoparticles. As evaporation takes place, the droplet’s shape changes, adding stress to the growing layer of nanoparticle residue. Cracking is one way to relieve that stress. Another method is delamination — peeling up from the surface. On the leftmost drop, the outer rim of nanoparticles delaminated — as seen from the circular fringes — which released stress without cracking. The rightmost drop, which had a smaller contact angle with the surface, couldn’t delaminate and instead cracked throughout. (Image credit: M. Ibrahim et al.)
In the Cheerios effect, floating objects can fall into one another due to capillary attraction — just like Cheerios link up in a cereal bowl. Here researchers play with that effect by adding repulsive magnets to their “cereal” pieces. They find that their so-called mermaid cereal falls into preferential spacing, with pieces pairing up but never touching. Adding lots of these pieces in a confined space creates interesting crystalline and striped patterns, as seen later in the video. (Video credit: A. Hooshanginejad et al.)
On the north shore of O’ahu, Hawaii, Banzai Pipeline is known for some of the most thrilling and deadly surfing in the world. The area’s barrel rolls are triggered when incoming waves break over the shallow reef. Photographer Kevin Krautgartner captures the waves from above, showcasing the incredible energy inherent in the ocean. The motion and texture of the water is mesmerizing. I feel like I could stare at these all day long! (Image credit: K. Krautgartner; via Colossal)
Explosives are used in many fields, including mining and demolition, but storing these devices is difficult and dangerous. Hundreds of accidents — many resulting in fatalities — have happened over the decades, simply because there is no true “off-switch” for explosive devices. But a group out of Los Alamos believe they’ve changed that.
Without water in the device, the outer surfaces burn, but no explosion takes place.
Using 3D-printing, the researchers built an explosive lattice filled with empty voids. With air in these gaps, any attempt to light the explosive fizzle. The outer layers of the explosive burn, but there’s no detonation. It is, relatively speaking, safe for storage.
When the voids are filled with water, the explosive detonates when lit.
But once the device is filled with water (or another liquid), the story is different. In this situation, the blast wave propagates and the explosive detonates, releasing 98% more energy than in its “storage” mode. Changing the liquid inside the device can enhance the explosive energy, too, which could allow users to tune the discharge. (Image credit: S. Moses; video and research credit: C. Brown et al.; via APS Physics)
Mussels live in rough conditions, constantly pummeled by waves and turbulent currents. They hold themselves fast in the flow using dozens of byssel threads (commonly called a mussel’s beard) that anchor them to rocks and other mussels. The threads get built within the mussel’s foot, the tongue-like protrusion mussels use to drag themselves. The threads are similar to our ligaments: strong and stretchy. Each one is cemented securely using an adhesive that hardens in water. If engineers could replicate that adhesive, it would be fantastic for use in medicine. (Video and image credit: Deep Look)
When you turn on your kitchen faucet, you may have noticed a big circle that forms on the bottom of the sink. This is a hydraulic jump, a region where fast-moving, shallow flow shifts to a slower-moving, deeper flow. Although these jumps start out circular, if the fluid is deeper than a critical value, the jump will break down and form polygons, like the one above. Exactly what shape the jump forms depends on many factors: flow speed, fluid depth, and flow history. The same flow conditions can even form more than one shape. But all of these shapes have one thing in common: their corners are universally around 114 degrees with a radius of 3.5 millimeters. (Image and research credit: S. Tamim et al.; via PRF)
A cylinder in a flow produces a series of alternating vortices known as a von Karman vortex street. Changing the flow speed and rotating the cylinder both allow researchers to tune the frequency of these shed vortices. What happens to an object in the wake?
For a simple hydrofoil tethered to the cylinder, the object wends back and forth along the vortices. But when that hydrofoil sits at the end of a double-pendulum, something very interesting happens. The whole apparatus follows a consistent trajectory similar to a human walking gait. Researchers are using this motion to build a robot that will help physical therapy patients regain a natural walking style. (Image and video credit: A. Carleton et al.)
