FYFD

Category: Phenomena

  • Featured Video Play Icon

    How N95 Masks Work

    You might imagine N95 masks as essentially a strainer intended to catch small particles, but as Minute Physics shows in this video, what these masks do is actually much more clever. A dense, strainer-like mask with tiny openings to block microscopic particles would be very tough to breathe through. Instead, N95 masks take advantage of one of the characteristics of tiny things: they’re very sticky. Thanks to van der Waals forces particles that touch a fiber will stick there.

    By creating an array of fibers between the particle and a person’s mouth, N95 masks do an excellent job of catching both large particles and tiny ones. They have a harder time with medium-sized particles because airflow around the fibers helps these particles avoid them.

    But, luckily, N95 masks have a solution for that problem, too. The fibers of the mask have an electric charge, which helps them attract particles of all sizes and capture them. Of course, as with all masks, they’ll work when worn as intended. (Video and image credit: Minute Physics)

  • Crocodilian-Inspired Aerodynamics

    Crocodilian-Inspired Aerodynamics

    Inspired by crocodilians, young scientist Angela Rofail designed attachments to reduce wind loads on high-rise buildings. When crocodilians swim, the ridges on their back help hide their motion from observation above the surface. Rofail wondered whether similar ridges would reduce the wind-induced swaying of high-rise buildings. Using a scale-model and crocodile-inspired knobs, the Year 10 student (read “high-school freshman” for U.S. readers) conducted wind tunnel tests that showed her modifications reduced drag on the model and kept it from moving in windy conditions. (Image credit: H. Roettger; video credit: CSIRO; via CSIRO; submitted by Kam-Yung Soh)

  • Searching For Solar Neutrinos

    Searching For Solar Neutrinos

    An experiment in Italy has reported new findings confirming a long-standing theory of nuclear fusion in our Sun. The researchers were able to detect neutrinos released by the relatively rare fusion of carbon and nitrogen. But catching those neutrinos took an impressive fluid dynamical feat.

    The Borexino solar-neutrino detector is essentially an enormous nylon balloon, filled with liquid hydrocarbons, immersed in water, and buried beneath a kilometer of rock. Most neutrinos fly through this milieu unhindered, but a few collide with hydrocarbon molecules, creating streaks of light picked up by the detector.

    The challenge in distinguishing solar carbon-nitrogen neutrinos comes from an isotope in the balloon’s nylon lining, which slowly leaks into the detector. The noise caused by the leaking isotope is easily confused with the true solar signal. To tamp down on that noise level, the researchers took elaborate steps to ensure that all 278 tonnes of liquid in the detector remained at exactly the same temperature, thereby eliminating convection in the detector. With only molecular diffusion to move the noisy isotopes, the researchers held the liquid incredibly still. One team member described the fluid as moving only tenths of a centimeter a month! (Image credit: NASA SDO; via Nature; submitted by Kam-Yung Soh)

  • Featured Video Play Icon

    How Well Do Masks Work?

    Many mixed messages have been spread about the efficacy of masks in preventing transmission of COVID-19. Nevertheless, there is good evidence that they help, as discussed in this video from It’s Okay to Be Smart. Much of the video shows schlieren imaging of a (healthy) individual engaging in regular activities – like talking, breathing, and coughing — with and without a cloth mask.

    Now, it’s important to note that what you see in these images is airflow, not the droplets that can carry the virus. However, research has shown that these airflows play a significant role in transporting droplets. It follows that disrupting those airflows can disrupt transmission of diseases passed via droplet. This is one of the key reasons to wear a mask.

    Notice how far jets and plumes of air fly from a maskless person’s mouth and nose. We cannot even observe how far momentum carries that air because the area visualized in this schlieren set-up is smaller than the full distance the air moves! But wearing a mask breaks up that flow structure. It reduces the air’s momentum, and it forces any air that does escape to move in smaller, less efficient structures. Even without considering any filtering effects or the fact that masks catch large droplets coming out of the wearer’s mouth, it’s clear that mask-wearing keeps others nearby safer. (Video and image credit: It’s Okay to Be Smart; references)

  • Featured Video Play Icon

    Ejecting Water from a Smartwatch

    Making electronics water-resistant can be a challenge, but as this Slow Mo Guys video demonstrates, engineers have some clever ways to deal with unwanted liquids. The Apple Watch, for example, uses its speakers to eject water that gets into the watch during immersion. As seen above, the vibration of the speakers ejects most of the water as tiny droplets. Occasionally, surface tension makes this tough and drops instead coalesce on the watch’s surface. To counter this tendency, the speakers sometimes pause, allowing water to collect before they begin vibrating again. (Video and image credit: The Slow Mo Guys)

  • Internal Waves in the Andaman Sea

    Internal Waves in the Andaman Sea

    Differences in temperature and salinity create distinct layers within the ocean. When combined with flow over submerged topography — underwater canyons, mountains, and reefs — it makes waves. But those waves aren’t always apparent when sitting at the surface. Instead, they travel along those ocean layers as internal waves that can be as tall as hundreds of meters in height.

    When the sun glints just right off the ocean, these massive internal waves can be caught by satellite imagery, as shown in the above image of the Andaman Sea near Thailand and Myanmar. Even seemingly calm waters can roil in the deep. (Image credit: USGS; via NASA Earth Observatory)

  • Featured Video Play Icon

    Traffic Flow and Phantom Jams

    We’ve all experienced the frustration of traffic jams that seem to come from nowhere — standstills that occur with no accident, construction, or obstacle in sight. Traffic shares a lot of similarities with fluid flows, including its waves and instabilities.

    These disturbances propagate and grow when traffic surpasses a critical density. Once that happens, any small speed adjustment made by a lead driver gets amplified by the larger and larger braking of each driver downstream. Effectively, this creates a wave of slower speed and higher density that travels downstream through the traffic.

    Each driver brakes more than the last largely because they can’t tell what the conditions upstream of them are. But that lack of knowledge may be less of an issue for driverless cars, which have the potential to communicate with cars and traffic sensors ahead of them. With enough automated vehicles on the highway, phantom traffic jams may become a thing of the past. (Video and image credit: TED-Ed)

  • New Details on the Sun’s Surface

    New Details on the Sun’s Surface

    As part of its shakedown, the new Inouye Solar Telescope has captured the surface of the sun in stunning new detail. Seen here are some of the sun’s turbulent convection cells, each about the size of the state of Texas. Hot plasma rises in the center of each cell, cools, and then sinks near the dark edges. Also visible within these dark borders are bright spots thought to mark magnetic fields capable of channeling energy out into the corona. Researchers hope the new telescope will help them uncover the physics behind these processes. (Image and video credit: Inouye Solar Telescope)

    Convection cells on the sun.

    Editor’s note: Like several other telescopes located in Hawai’i, the Inouye Solar Telescope was built against the wishes of many native Hawaiians. Although FYFD supports scientific progress, it is my personal belief that scientific advances should not come at the expense of indigenous populations. I strongly urge my scientific colleagues to listen to and work alongside those with concerns about future facilities.

  • Featured Video Play Icon

    Celebrating Turbulence

    Laminar flow is easy to love, but turbulence is a far richer phenomenon. That’s the premise behind Veritasium’s new video (and, yes, I agree with him). In the video Derek provides a nice introduction to turbulence, including a checklist of qualities a turbulent flow must have.

    Personally, I don’t classify flows as simply being either laminar or turbulent; I view those two states as ends of a spectrum, which means there are many flows that fall somewhere in-between. (For more on what happens between laminar and turbulent, check out my video on transition.)

    As neat and eye-catching as laminar flow can be, turbulence is critical to life as we know it. It’s a necessary ingredient in cloud and raindrop formation. It drives the mixing of blood in our hearts. It keeps the leaves on trees from overheating. Without it, your coffee would be cold long before your cream mixes in. Turbulence is even critical to star formation; without turbulence, our entire solar system might have lacked the matter and time necessary to form! (Video and image credit: Veritasium)

  • Toad Singing

    Toad Singing

    With spring heading into summer, many parts of the United States enjoy a nighttime chorus of frogs and toads. These amphibians are singing to attract mates and delineate territory. Some, like this American toad, sing from the water, and the vibration of their vocal sac creates ripples that last as long as they’re vocalizing. The toad sings by closing its nostrils and mouth, then forcing air from its lungs over its vocal cords. Those vibrations are amplified by resonance in its vocal sac, generating the high chirp we hear. (Image credit: cassiescisco)