FYFD

Tag: biology

  • The Best of FYFD 2025

    The Best of FYFD 2025

    Happy 2026! This will be a big year for me. I’ll be finishing up and turning in the manuscript for my first book — which flows between cutting edge research, scientists’ stories, and the societal impacts of fluid physics. It’s a culmination of 15 years of FYFD, rendered into narrative. I’m so excited to share it with you when it’s published in 2027.

    As always, though, we’ll kick off the year with a look back at some of FYFD’s most popular posts of 2025. (You can find previous editions, too, for 2024, 2023, 2022, 2021, 2020, 2019, 2018, 2017, 2016, 2015, and 2014.) Without further ado, here they are:

    What a great bunch of topics! I’m especially happy to see so many research and research-adjacent posts were popular. And a couple of history-related posts; I don’t write those too often, but I love them for showing just how wide-ranging fluid physics can be.

    Interested in keeping up with FYFD in 2026? There are lots of ways to follow along so that you don’t miss a post.

    And if you enjoy FYFD, please remember that it’s a reader-supported website. I don’t run ads, and it’s been years since my last sponsored post. You can help support the site by becoming a patron, buying some merch, or simply by sharing on social media. And if you find yourself struggling to remember to check the website, remember you can get FYFD in your inbox every two weeks with our newsletter. Happy New Year!

    (Image credits: droplet – F. Yu et al., starlings – K. Cooper, espresso – YouTube/skunkay, fountain – Primal Space, Uranus – NASA, turbulence – C. Amores and M. Graham, capsule – A. Álvarez and A. Lozano-Duran, melting ice – S. Bootsma et al., puquios – Wikimedia, cooling towers – BBC, solar wind – NASA/APL/NRL, Lake Baikal – K. Makeeva, sprite – NASA, roots – W. van Egmond, sunflowers – Deep Look)

    1. I know what I did. ↩︎
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  • Lung Flows

    Lung Flows

    When a fluid coats the inner walls of a cylinder, it can move downward in what’s called a collar flow. In our airways, a sinking collar flow can thicken as it falls, eventually blocking the airway completely.

    In a Newtonian fluid, this thickening during motion is essentially unavoidable; any small disturbance to the fluid will make its thickness change. But in a viscoplastic fluid–one more akin to the mucus in our airways–researchers found that, below a critical film thickness, the collar flow won’t thicken to form a blockage. (Image and research credit: J. Shemilt et al.; via APS)

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    Ripple Bugs

    Ripple bugs are a type of water strider capable of moving at a blazing fast 120 body lengths per second across the water surface. In addition to their speed, ripple bugs are incredibly agile and are active almost constantly. Researchers believe they’ve found the insect’s secret: feather-like hydrophilic fans that spread on contact with the water. These fans help the insects push off the water and steer, but they require no effort to open and close. They’ve even adapted the technique to bio-inspired robots and seen improvements in speed, agility, and efficiency. (Video credit: Science; research credit: V. Ortega-Jimenez et al.)

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    Leaves Dance in the Wind

    Once a breeze kicks up, leaves on a tree start dancing. Every tree’s leaves have their own shapes, some of which appear very different from other trees. But their dances have patterns, as this video shows. In it, researchers explore how leaves of different shapes deform in the wind and how they can decompose that motion to compare across leaves. (Video and image credit: K. Mulleners et al.; via GFM)

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  • Controlling Hovering

    Controlling Hovering

    Hummingbirds and many insects hover when feeding, escaping predators, and mating. While scientists have decoded the mechanics of a hummingbird’s figure-8-like hovering wingstroke, it’s been harder to understand how the creatures control their hovering. Most of our attempts to control hovering require more computational power than hummingbirds and insects are thought to have. But this study describes a new control scheme: one that allows stable, real-time hovering with little computational cost. (Image credit: J. Wainscoat; research credit: A. Elgohary and S. Eisa; via APS)

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  • In Deep Lakes, Mixing is Disappearing

    In Deep Lakes, Mixing is Disappearing

    With a depth of nearly 600 meters, Crater Lake in Oregon is the deepest lake in the United States. It’s known for its brilliant blue hue and startling clarity. But, like other deep lakes, Crater Lake is changing as temperatures warm. It’s edging ever closer to a day where its deep, cold waters no longer mix.

    Although the details of mixing vary from lake to lake, older records show that most deep lakes would overturn and fully mix on a frequency that ranged from twice a year to every seven years. This overturning happens when winds push frigid, near-frozen water. As that water approaches the shoreline, it gets forced downward, where the pressure at depth makes the cold water denser still, causing it to sink beneath the warmer water layer near the lake bottom. That kicks off larger-scale mixing that redistributes oxygen, nutrients, and toxins in the lake.

    When this regular mixing stops, the entire ecosystem gets affected. Over time, oxygen gets depleted in deeper in the lake, leaving a dead zone unable to support fish and other aquatic life. Meanwhile, longer and warmer growing seasons favor phytoplankton and algae that cloud the waters and disrupt a lake’s unique ecology.

    For a much more detailed look at deep lake mixing and the changes we’re seeing, check out this article over at Quanta Magazine. It’s a longer read but well worth your time. (Image credit: N. Perez Aguilar; see also: Quanta Magazine)

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  • Deep Breaths Renew Lung Surfactants + A Special Announcement

    Deep Breaths Renew Lung Surfactants + A Special Announcement

    Taking a deep breath may actually help you breathe easier, according to a new study. When we inhale, air fills our alveoli–tiny balloon-like compartments within our lungs. To make alveoli easier to open, they’re coated in a surfactant chemical produced by our lungs. Just as soap’s surfactant molecules squeezing between water molecules lowers the interface’s surface tension, our lung surfactants gather at the interface and lower the surface tension, making alveoli easier to inflate.

    But things are a little more complicated in our lungs than in our kitchen sink because of our constant cycle of breathing, which stretches and compresses our lungs’ surfaces and surfactant layers. Imagine a flat interface, lined with surfactant molecules; then stretch it. As the interface stretches, gaps open between the surfactant molecules and allowing molecules from the interior of the liquid to push their way to the newly stretched interface, changing the surface tension. If the interface gets compressed, some of the excess molecules will get pushed back into the liquid bulk.

    In looking at how lung surfactants respond to these cycles of compression and stretching, the researchers found that the lung liquid develops a microstructure during cycles of shallow breathing that makes the surface tension higher, thus making lungs harder to fill. In contrast, a deep breath like a sigh replenished the saturated lipids at the interface, lowering surface tension and making lungs more compliant. So a deep sigh actually can help you breathe easier. (Image credit: F. Møller; research credit: M.. Novaes-Silva et al.; via Gizmodo)

    P.S. — I’ve got a book (chapter)! Several years ago, I joined an amazing group of women to write two books (one for middle grades and one for older audiences) about our journeys as scientists. And they are out now! In fact, today we’re holding a “Book Bomb” where we aim for as many of us as possible to buy the book(s) on the same day. If you’d like to join (and get ahead on your gift shopping), here are (affiliate) links:

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  • Spores Get a Lift

    Spores Get a Lift

    Mushrooms have the challenging task of dispersing spores, typically from heights no more than a few centimeters above the ground. At that altitude, viscosity and friction with the ground mean that air barely moves, if it does at all. And mushrooms rely on a wide range of methods, from explosive launches to rain assistance to making their own weather. Every one of these methods gives spores a lift in altitude to reach higher winds and greater dispersal. (Image credit: A. Bejczi/CUPOTY; via Colossal)

  • Fluids at the Angstrom-Scale

    Fluids at the Angstrom-Scale

    We spend our lives dealing with fluids at a scale where the motion of individual molecules is beneath our notice. There’s no reason to track every molecule of water moving through a municipal pipe; it’s effectively impossible, anyhow! But once you are dealing with pipes that are small enough–below about 1 nanometer in diameter–fluids have to be considered molecule-by-molecule. At this scale, so-called angstrofluidics behave very differently.

    Intuition suggests that flow through such tiny channels would be extremely slow, however researchers have observed protein channels that allow a single water molecule through at a time while still processing a billion molecules each second. Combine this throughput with charged channel walls that can sort molecules by polarity, and angstrofluidics offers the possibility for unprecedented control for filtering, desalination, and drug testing. (Image credit: T. Miroshnichenko; see also R. Boya et al.)

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  • Why Sharper Knives Mean Fewer Onion Tears

    Why Sharper Knives Mean Fewer Onion Tears

    Onions are a well-known source of tears for many a cook. And while the chemical source of their power–onions release a chemical that reacts in our eyes to produce tears–has been known for years, no one has looked at the fluid dynamics in the process until now.

    Video of droplets sprayed as a knife cuts into an onion.

    As seen above, a knife piercing the onion’s surface releases a mist of high-speed droplets, followed by a slower spray. Much like a citrus fruit’s microsprays, the onion’s fountain depends on both solid and fluid mechanics. As the knife presses into the onion’s stiffer outer layer, pressure builds in the softer layer underneath, which contains pores of fluid. Once the knife breaks the epidermis, that pressurized fluid sprays out.

    The good news is that the team also confirmed a common culinary wisdom: using a sharper knife and a slower, gentler cut will reduce the spray and its speed, resulting in fewer tears. (Image credit: M. Stone; research credit: Z. Wu et al.)

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