Japanese Engineers Design Automatic Tsunami Gate

Sketch of the design for the automatic tsunami gate. Source: Takagi et al, Renewable Energy 219 (2023) 119563

Researchers based at the Tokyo Institute of Technology have proposed a simple yet efficient way to protect ports from tsunamis – a self-closing gate that is powered by changes in tides. While such gates, known as “seawalls,” already exist, the trouble with them has been that they need power to operate. But tsunamis are often an aftermath of storms, torrential rains, waves, and earthquakes that lead to power outages, making the seawalls inefficient. The team solved the problem by making the gate battery powered, and constantly replenishing the gate’s battery from tidal changes.The team assessed the feasibility of the system and found that it could be deployed at 14 ports in Japan. Press release here. Full article here.

This episode of Science News covers how X-rays were discovered. The first three explanations didn't make any sense to me and before I knew it, I had 12 books about Wilhelm Röntgen on my desk because my brain is a wild place. I eventually figured out what must have happened, I believe, and thought you might find it interesting, too. You can take the quiz here.

Underwater Sprinkler Solved Or: Feynman (and Mach’s) Reverse Sprinkler Solved

Left: Screen capture from video of experiment: Fluorescent dye traces the flow pattern as the submerged part of the device expels water then reverses to sucking mode, revealing central vortices and complex flow-patterns. Image Credit: K. Wang et al., “Centrifugal flows drive reverse rotation of Feynman’s sprinkler,” Phys. Rev. Lett. 132, 044003 (2024). Right: Public domain DALL-E3 generated image of Richard Feynman and sprinkler, which made me laugh for what it’s worth.

In 1966 Richard Feynman proposed a whimsical thought experiment: in which direction would an S-shaped lawn sprinkler rotate if it was submerged underwater and the flow was reversed inwards? While variations of this problem had sparked intense debate since Ernst Mach’s treatment in The Science of Mechanics in 1883, and although young graduate student Richard Feynman’s inconclusive version of the experiment blew up from internal pressure (a la the theorist’s "Pauli effect”), sending glass everywhere, a recent, more careful experiment has provided the ultimate definitive answer: as Feynman suspected, the flow reverses!  The team addressed previous experimental concerns by allowing the sprinkler’s S-shaped arms to auto-rotate with minimal friction by letting it float freely in water. The team could then adjust the flow direction by raising or lowering a water tank connected to the center of the hub. The experiment ran for several hours to ensure accuracy. The team collected detailed maps of fluid flow patterns that were lit up via laser-activated fluorescent dye microparticles suspended in the fluid. They discovered that the reverse jets are not directed precisely at the center because of the distortion of the hydrodynamic flow as it passes through the curved arms of the S-sprinkler. As water flows around the arms, it is then slung outward by centrifugal force, which creates interesting asymmetric flow patterns and ultimately reverses the direction of flow. While the reverse sprinkler might seem like merely fun and games, the problem is relevant in fluid mechanics applications and technologies harnessing energy from air and water. Watch a video here, read a review article here, and the full paper is here.

The Moon is Shrinking, And It’s a Problem for Astronauts

Left: Fault lines formed on the moon’s surface as a result of the moon’s shrinkage. Image Credit: NASA. Right: cartoon of the Moon shrinking. (JL Nielsen with DALL-E3, CC-BY SA 4.0)

It may sound like sheer lunacy, but wrinkles in the Moon’s surface detected by NASA’s Lunar Reconnaissance Orbiter (LRO) suggest the Moon is on a cosmic diet. NASA estimates that it has shed more than 46 meters (that’s 1,800 inches!!!) of its “waistline” circumference over the last several hundred million years. The major cause for this shrinkage, geologists think, is a combination of the continued cooling of the moon and the tidal forces from the Earth’s gravitational field.Recently, a team of scientists based at the Smithsonian Institute’s Center for Planetary Studies has explored the side effects our moon is experiencing from its crash diet, including tectonic shifts and surface creasing that’s causing the formation of fault lines where sections of crust collide. The paper pinpoints significant warping in the moon’s south polar region, an area that has already been earmarked for NASA’s potentially human-crewed Artemis III landings. This area sometimes experiences moonquakes that last for hours. The researchers say that it could also see landslides, which could potentially pose a threat to both robotic and human explorers or settlers. Watch a NASA video about moon shrinkage here, read related press releases here, here, and here, and find relevant papers here and here.

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