FYFD

Tag: fluid dynamics

  • Featured Video Play Icon

    “Timedrift II”

    As a teenager, I climbed Mount Kilimanjaro. The final ascent began around midnight, and we climbed through the dark, through sunrise, and into the early morning. I remember pausing at one point, just as the sun was rising, and looking out at the clouds thousands of meters below. From that height, they looked like an ocean, rippled with lavender waves. Timelapse films like this one, by filmmaker Martin Heck, remind me of that morning and the sense that I had of the sky as an ocean, flowing, crashing, and surging in ways we cannot appreciate until we slow down and look closer. (Image and video credit: M. Heck/Timestorm Films)

  • Rotating Waves of Grains

    Rotating Waves of Grains

    Rotating drums are a popular way to explore granular dynamics. Here, researchers fill a cylinder (seen below) with heavy grains and a low-viscosity fluid, then rotate the mixture about a horizontal axis. This sets up a contest between centrifugal forces and gravitational forces on the grains. At the right rotation rates, the grains form annular rings around the outside of the cylinder, where they rotate at a different speed than the fluid. This difference in speed between the two layers can trigger a Kelvin-Helmholtz instability and cause waves along the interface between the grains and the fluid, as seen in the examples above. (Image and research credit: V. Dyakova and D. Polezhaev; top image adapted by N. Sharp)

    Image of the experimental apparatus when not rotating.
  • Featured Video Play Icon

    Inside a Metal Vortex

    What do you get when you combine liquid gallium, a blender, and a special probe lens? Some pretty wild slow-mo video of a liquid metal vortex, courtesy of the Slow Mo Guys. This video is almost as notable for its set-up as it is for the high-speed footage, given the lengths Gav and Dan go to in order to get the shot! (Image and video credit: The Slow Mo Guys)

  • Neptune’s Seasonal Changes

    Neptune’s Seasonal Changes

    Ice giant Neptune orbits our sun once every 165 years, meaning that each season on the planet lasts about 41 years here on Earth. Currently, the side of Neptune facing us is entering early summer, but a recent survey of atmospheric measurements show that Neptune’s stratosphere is experiencing some unexpected changes. Between 2003 and 2018, the team found that global stratospheric temperatures actually decreased by 8 degrees Celsius. Even more dramatically, Neptune’s southern pole warmed by a full 11 degrees Celsius between 2018 and 2020. Both results hint that atmospheric patterns on the planet may be far more complex than current models assume. (Image credit: NASA/JPL; research credit: M. Roman et al.; via Physics World)

  • Featured Video Play Icon

    Escaping the Flood

    Fire ants clump together into giant rafts to stay alive during floods. But these rafts won’t form with just any number of ants. Researchers found that individual ants will actually kick one another away. It’s not until there are about ten ants that the raft formation becomes stable. In this video, the team lays out their experiments and models for fire ant rafting, showing that capillary action helps draw the raft together and individual ants’ activity can destabilize rafts if they’re too small. (Image and video credit: H. Ko and D. Hu)

  • “Metamorphe”

    “Metamorphe”

    A smoke-like haze drifts over surreal landscapes in the “Metamorphe” series by Reuben Wu and Jenni Pasanen. Though fluidic in appearance, these pieces are a merger between Wu’s drone light photography and Pasanen’s AI-assisted digital creations. Even so, the images are extremely evocative of fluid motion, connected as they are to human senses (like smell, hearing, and touch) that often rely directly on fluid dynamics. For more, check out the artists’ sites and Instagram. (Image credits: R. Wu and J. Pasanen; via Colossal)

  • Swimming Together

    Swimming Together

    Scientists have long pondered the possibilities of hydrodynamic benefits to the ways fish school. But most analyses of schooling have assumed a fixed spacing that’s far more orderly than what we observe in nature. In this experiment, researchers instead used a pair of robotic swimmers (essentially hydrofoils) to explore a range of swimming formations. What they found was a map of places where a second swimmer could easily “lock in” to a position relative to the leader and have their positioning stabilized by interactions with the leader’s wake (lower image). Interestingly, the beneficial regions extend much further downstream for fish positioned diagonally to the leader than they do for one directly following. With such a wide range of easily-stabilized following positions, it’s no wonder that schools of fish are amorphous instead of strictly crystalline! (Image credit: top – S. Pena Lambarri, map – J. Newbolt et al.; research credit: J. Newbolt et al.)

    The shaded areas of this map represent areas where a second swimmer can passively "lock-in" relative to the leader's position, shown in gray. This data is based on tests with robotic swimmers.
    The shaded areas of this map represent areas where a second swimmer can passively “lock-in” relative to the leader’s position, shown in gray. This data is based on tests with robotic swimmers.
  • Featured Video Play Icon

    How Dunes Form

    On its face, the idea that sand and wind can come together to form massive mountainous dunes seems bizarre. But dunes — and their smaller cousins, ripples — are everywhere, not just on Earth but on other planetary bodies where fine particles and atmospheres interact. In this video, Joe Hanson gives a great overview of sand dynamics, beginning with what sand is, how it moves, and what it can ultimately form. It’s well worth a watch, even if you know a little about dunes already; I know I learned a thing or two! (Image and video credit: Be Smart)

  • You’re Drunk, Toadlet

    You’re Drunk, Toadlet

    Most frogs and toads are excellent jumpers, taking off and landing with a control and grace that rivals elite athletes. Not so for the pumpkin toadlet. These species have become so miniaturized that the structures of their inner ears are too narrow for the fluid flow that helps frogs (and humans!) orient themselves in space. So while the toadlet certainly can jump, it careens through the air drunkenly and lands in any old direction. It’s hard not to laugh at their belly flops, somersaults, and straight-up head-first crashes. Fortunately, being so small, these landings don’t seem to hurt the toadlets, but one imagines they’re unpleasant nevertheless. Left to their own devices, the pumpkin toadlet prefers walking, slowly, like a chameleon; it might be the only way to stay within the limits of its inner ear. (Image credits: top – S. Kikuchi, others – R. Essner, Jr. et al.; research credit: R. Essner, Jr. et al.; via The Atlantic; submitted by Kam-Yung Soh)

  • Featured Video Play Icon

    Rifts in Rafts

    A raft of particles floating on water has some natural cohesion from particle attraction and capillary action. But when the raft is pulled apart, what happens? Does it break cleanly in one spot? Does it stretch and deform? That’s what this video explores. It turns out that the speed you pull the raft at determines how it holds together. Every particle cluster has a preferred relaxation rate, and by choosing the pulling speed, you determine which relaxation rate — and therefore cluster size — can survive most effectively. (Image and video credit: K. Tô and S. Nagel)