FYFD

Category: Phenomena

  • Infrasound Fire Suppression Goes Commercial

    Infrasound Fire Suppression Goes Commercial

    Sprinklers have long been the go-to fire protection for commercial properties and some residences. Dousing a fire in water not only puts out the flames but cools the surroundings and helps prevent reignition. But it requires complicated infrastructure and can damage buildings and their contents. Back in 2015, students were experimenting with an alternative fire extinguisher that used sound below the range of human hearing; now a company is pitching a version of that technology for replacing sprinklers.

    As described by Ars Technica, this infrasound system can detect and put out a small kitchen fire in under a minute. But fire fighting experts warn that there’s a big difference between a fire small enough for a fire extinguisher to handle and the kinds of fires sprinklers put out. With lives at stake, the burden of proof is significant for Sonic Fire Tech and any other company that wants to get their infrasound “sprinkler” system cleared for use in buildings. (Image credit: I. Azevedo; via Ars Technica)

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  • Seeking Quieter Supersonic Flight

    Seeking Quieter Supersonic Flight

    Supersonic flight over the U.S. has been banned by all non-military aircraft for more than fifty years. The ban gained momentum in the 1960s after test programs over St. Louis and Oklahoma provoked public outcry. But NASA’s X-59 aircraft is working to lift the ban by softening the sonic booms that encouraged the ban in the first place. Although it hasn’t been tested at supersonic speeds yet, pilots are putting the sharp and skinny X-59 through its paces, slowly widening the flight envelope.

    In the video above, NASA shares footage of some of the recent test flights, including various maneuvers like phugoids, banking rolls, flutter, and landing gear tests. Pay close attention to the pilot’s view and the radio chatter, and you’ll hear that they’re hovering around Mach 0.98 in some cases–just underneath the point of generating a shock wave around the aircraft. It will be neat to see what happens when they finally do go supersonic. Will it be as quiet as promised? (Video credit: NASA; image credit: NASA/L. Losey; see also NASA; via Gizmodo)

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  • Blue Jewels and Gray Haze

    Blue Jewels and Gray Haze

    Beginning in early spring, brilliant blue ponds form on Greenland’s ice sheets as meltwater gathers in indentations. This satellite image shows the ice east of Nordenskiöld Glacier, which is the tongue of ice projecting on the left side of the image. The center region of ice is darker, marked by soot, ash, and dirt left behind after previous ice layers have melted. These darker remains make the ice less reflective to sunlight; with less reflectivity, the ice absorbs more sunlight, melting faster. (Image credit: M. Garrison/NASA Earth Observatory)

    A satellite image of Greenland's ice sheet, showing jewel-toned blue meltwater ponds to the right, a haze of dirty ice in the center, and bare rock and open water to the left.
    A satellite image of Greenland’s ice sheet, showing jewel-toned blue meltwater ponds to the right, a haze of dirty ice in the center, and bare rock and open water to the left.
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  • Herring Spawn

    Herring Spawn

    From mid-February to early May, tiny silvery Pacific herring gather along the shallow coastlines of Vancouver Island off British Columbia, Canada. In these sheltered waters, they spawn; female fish produce sticky eggs and males flood the area with milt, which turns the water a milky turquoise or green. The colors can be so vivid that the spawn is visible to satellites.

    Barkley Sound, on the island’s southwestern side, frequently hosts spawning, as its rocky shoreline provides protection and the pockets of lower salinity that the fish favor. After spawning, the fish migrate back to their feeding grounds in deeper, nutrient-rich waters. (Image credit: R. Cutler; via NASA Earth Observatory)

    A herring spawn clouding the waters along Vancouver Island on February 16, 2026.
    A herring spawn clouding the waters along Vancouver Island on February 16, 2026.
    A herring spawn event near Forbes Island in Barkley Sound turns the shoreline green.
    A herring spawn event near Forbes Island in Barkley Sound turns the shoreline green.
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  • Setting the Stripes on a Tiger (Cake)

    Setting the Stripes on a Tiger (Cake)

    A tiger skin cake forms a distinctive pattern of light and dark patches as it bakes. Its current popularity seems to have expanded outward from China; I found a lot of Swiss-roll-style recipes that use it as an outer wrapper. Here, researchers look at how the wrinkled surface forms. The viscous batter quickly forms a solid skin on its surface, and, as the cake grows, the skin is forced to bend and wrinkle to accommodate the growth. Interestingly, the length-scale of the wrinkling pattern depends on the batter’s depth. For larger stripes, use a thicker layer of batter! (Image credit: K. Koutova et al.)

    Research poster showing the wrinkling pattern formed on a tiger skin cake.
    Research poster showing the wrinkling pattern formed on a tiger skin cake.
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  • Supersonic Jet Interaction

    Supersonic Jet Interaction

    When supersonic jets get emitted into rarefied air, they behave differently than they do in regular atmospheric conditions. Here, researchers picture three different configurations these jets can take. In the top image, the jets are close enough together that they appear to merge into a narrow supersonic jet. In the middle image, the jets are not quite as close together. They merge but form what appears to be a subsonic wake. In the final image, the jets are far enough apart that they don’t merge, although they do appear to “lean in” toward one another. (Image credit: S. Lee et al.)

    Research poster showing two supersonic jets interacting in a rarefied atmosphere.
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    Seeing Stress in an Avalanche

    Researchers sometimes study avalanches and other granular flows in a rolling drum, where grains can cascade down continuously. Here, the twist is that they’ve done it with photoelastic disks, which show stress patterns when viewed under crossed polarizing filters.

    In any given moment, the contacts between neighboring particles form a force chain that lights up the disks. In motion, the effect resembles lightning forking and branching across the sky. The close-ups of stress reverberating during impact are especially mesmerizing. (Video and image credit: R. Hodgson et al.)

    Animation of stress reverberating through particles as they roll in a drum.
    Animation of stress reverberating through particles as they roll in a drum.
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  • Liquid Pulleys and Gears

    Liquid Pulleys and Gears

    In mechanical systems, gears and pulleys transmit rotation from one location to another. Here, researchers explore a fluid dynamical version of such systems. The set-up consists of two rotors contained in a cylindrical corral filled with a water-glycerin mixture. One of the rotors is active, marked here with orange; the other (blue) one is passive, meaning that it can rotate due to the forces on it but it is not actively driven by a motor.

    The three flow visualizations illustrate different configurations the rotors can take on, depending on their separation distance. In the top image, the rotors have a moderate separation distance and the passive one rotates opposite of the active one. That rotation direction is set by the high-shear flow on its inner side. If the rotors are close together (left image), they rotate in the same direction, aided by strong shear on the outside edge of the passive rotor; this mimics being linked with a belt. And, finally, if the rotors are widely separated, they also corotate, with the fluid in between acting like a virtual gear linking them. (Image credit: J. Smith et al.)

    Research poster showing how an active and a passive rotor can be paired through hydrodynamic interactions.
    Research poster showing how an active and a passive rotor can be paired through hydrodynamic interactions.
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    Plucking Droplets

    A sudden breeze can pluck droplets hanging from a stem. Here, researchers recreate that phenomenon in the laboratory. With a close-up view and high-speed images, we can enjoy every detail of the detachment and break-up. As the wire pulls away, it drags a liquid sheet off the droplet. The thicker rims on either side of the sheet eventually collide, creating a jet that stretches, deforms, and, at last, breaks. (Video and image credit: D. Maity et al.)

    Animation of two droplets getting plucked, one made of glycerin+water (left) and one of water (right).
    Animation of two droplets getting plucked, one made of glycerin+water (left) and one of water (right).
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  • Meandering Along the Alabama River

    Meandering Along the Alabama River

    Over time, rivers naturally curve and meander. As water accelerates around a river bend’s curve, it creates a secondary flow that carves sediment away from the outer bank and deposits it on the inner one. That, in turn, makes the river bend sharper until it eventually cuts part of the river off into an oxbow lake. In this astronaut photo, we see the Alabama River flowing right-to-left. The river’s natural meander is constrained by the dam on the center left, which widens the river upstream. The higher water level upstream creates the feather-like floodplains lining the river. (Image credit: NASA; via NASA Earth Observatory)