FYFD

Category: Research

  • Mossy Vortex Rings

    Mossy Vortex Rings

    Many plants have evolved an ability to move remarkably quickly. Often, this capability is driven by water. Here we see the moss Sphagnum affine, which disperses its spores explosively. The process is triggered by the spore capsule gradually drying out; its shape changes from round to cylindrical, pressurizing the capsule. Once the internal pressure is high enough to overcome the strength of the capsule’s upper membrane, the capsule bursts, sending a plume of spores aloft. The sudden release of spore-laden air forms a vortex ring, which lifts the spores higher far more efficiently than they would be otherwise. (Image credit: capsule dry-out – J. Edwards et al., spore dispersal – J. Edwards et al. 2010; research credit: J. Edwards et al.)

  • Scaling High-Speed Impacts

    Scaling High-Speed Impacts

    The impact of a solid object into a bed of grains is a major topic in many fields from ballistics to astronomy. Researchers study these impacts experimentally using photoelastic disks, which display visible stress patterns when placed between polarizers. The lightning-like patterns you see above reveal how forces propagate inside the grains as the object hits.

    Researchers focused on the peak forces generated during high-speed impacts, an area that hasn’t been well-captured by existing impact models. They found that this peak force obeys its own scaling laws that depend on factors like impact speed, impacter size, grain stiffness, and grain density. (Image and research credit: N. Krizou and A. Clark)

  • Dissolving Caramel

    Dissolving Caramel

    In nature, erosion patterns are driven by the interactions of flow and topography. Here, researchers study that process in the lab by placing an inclined block of caramel in quiescent syrup and watching as it dissolves. Initially, the bottom surface of the block develops regularly-spaced plumes — the dark lines seen in the first image. But because the caramel-laden plumes are heavier than the surrounding fluid, the flow quickly becomes unstable. The plumes cross one another and begin to carve chevrons into the caramel.

    The chevrons appear to march their way upward in the video. They slowly grow and change into a distinctly scalloped pattern. Scallops like these are often seen by geologists in caves and icebergs, and the authors argue that their results and modeling indicate the importance of buoyant flow effects on such natural formations. (Image and research credit: C. Cohen et al.)

  • Measuring Contaminants in Drops and Bubbles

    Measuring Contaminants in Drops and Bubbles

    Rising bubbles and droplets are common in many chemical and industrial applications. But just a tiny concentration of contaminants on their surface can completely alter their behavior, disrupting coalescence and slowing down chemical reactions.

    Historically, it’s been hard to measure the level of contamination in these some drops and bubbles, but a new study outlines a way to measure these small concentrations by perturbing the drops and watching how they deform. By analyzing how the drop shimmies and shakes, they’re able to measure its surface tension and, ultimately, the concentration of contaminants. (Image credit: S. Sørensen; research credit: B. Lalanne et al.; via APS Physics)

  • Jupiter in Infrared

    Jupiter in Infrared

    This stunning new image of Jupiter in infrared is part of a data set combining measurements from ground- and space-based observatories. The glowing Jovian orb seen here is a composite of some of the sharpest images captured by the Gemini North Telescope’s Near-Infrared Imager from its perch on Mauna Kea. The brightest areas correspond to warmer temperatures over thinner, hazier clouds, whereas the dark areas mark towering, thick clouds.

    The ground-based images — and observations from Hubble — were timed to coincide with passes from the Juno spacecraft. This combination of infrared, visible light, and radio wave observations gives scientists an unprecedented look at Jovian atmospheric processes. It revealed, for example, that lightning measured by Juno deep inside Jupiter’s atmosphere corresponded to convective storm cores visible to the other imagers. The combination of observations allowed the researchers to reconstruct the structure of these Jovian storms in a way that no single instrument could reveal. No doubt planetary scientists will learn lots more about Jovian convection from the data set. (Image credit: Jupiter – International Gemini Observatory/NOIRLab/NSF/AURA, M.H. Wong (UC Berkeley)/Gizmodo, illustration – NASA, ESA, M.H. Wong (UC Berkeley), and A. James and M.W. Carruthers (STScI); research credit: M. Wong et al.; via Gizmodo)

  • Featured Video Play Icon

    Exploring Martian Mud Flows

    When looking at Mars and other parts of our solar system, planetary scientists are faced with a critical question: if what I’m looking at is similar to something on Earth, did it form the same way it does here? In other words, if something on Mars looks like a terrestrial lava flow, is it actually made of igneous rock or something else?

    To tackle this question, a team of researchers explored mud flows in a pressure chamber under both Earth-like and Martian conditions. They found that mud flowed quite freely on Earth, but with Martian temperatures and pressures, the flows resembled lava flows like those found in Hawaii or the Galapagos Islands.

    On Mars, mud begins boiling once it reaches the low pressure of the surface. This boiling cools it, causing the outer layer of the mud to freeze into an increasingly viscous crust, which changes how the mud flows. In this regard, it’s very similar to cooling lava, even though the heat loss mechanisms are different. (Video and research credit: P. Brož et al.; image credit: N. Sharp; see also P. Brož; submitted by Kam-Yung Soh)

  • New Signs of Turbulence in Blood Flow

    New Signs of Turbulence in Blood Flow

    Our bodies are filled with a network of blood vessels responsible for keeping our cells oxygenated and carrying away waste products. In many ways, our blood vessels are tiny pipes, but there’s a crucial difference in the flow they carry: it’s pulsatile. Because the flow is driven by our hearts, rather than a continuous pump, every heartbeat creates a distinct cycle of acceleration and deceleration in the flow. And new research has found that this cycle, when combined with curvature or flow restrictions like plaque build-up, can create turbulence in unexpected places.

    Specifically, the researchers found that decelerating pipe flows can develop a helical instability that breaks down into turbulence, even in vessels where purely laminar flow would be expected. In the animations above, you can see the flow slow, develop swirls and then break into turbulence. The flow becomes laminar again as it accelerates, but during that brief bout of turbulence there’s much higher forces on the walls of a blood vessel. Over time, that extra force could contribute to inflammation or even hardening of the arteries. (Image and research credit: D. Xu et al.; via phys.org)

  • Particle-filled Splashes

    Particle-filled Splashes

    Adding particles to a liquid can significantly alter its splash dynamics, as shown in this new study. In the first image, a purely-liquid droplet spreads on impact into a thin liquid sheet that destabilizes from the rim inward, ripping itself into a spray of droplets. At first glance, the particle-filled droplet in the second image behaves similarly; it, too, spreads and then disintegrates. But there are distinctive differences.

    During expansion, the particles increase the drop’s effective viscosity, meaning that the splash sheet does not expand as far. That apparent viscosity increase is also part of why the drops the splash sheds are bigger than those without particles. The other part of that story comes from the retraction, where the variations in thickness caused by the particles and their menisci create preferential paths for the flow. As a result, the particle-filled splash breaks up faster and into larger droplets compared to its purely-liquid counterpart. (Image and research credit: P. Raux et al.)

  • Fractal Flame Propagation

    Fractal Flame Propagation

    Hydrogen is a promising alternative to carbon-based fuels, but it comes with its own special challenges. Hydrogen gas is extremely flammable, including under circumstances that would normally quench flames, as shown in this recent study.

    What you see above are water condensation patterns left behind after the passage of hydrogen flames through a narrow gap between two glass plates. With other fuels, the narrow confinement and low fuel ratio used in these experiments would keep the flames from spreading. But because hydrogen is so light, it diffuses much faster than other fuels, allowing it to spread in these fractal patterns despite its confinement. Engineers will have to account for hydrogen’s easy spread when designing containment strategies. (Image and research credit: F. Veiga-López et al.; via APS Physics)

  • Bubble Dynamics Govern Faster Pouring

    Bubble Dynamics Govern Faster Pouring

    We’re all familiar with the problem of pouring a liquid from a narrow-necked bottle. To a certain extent, tilting the bottle further will reduce the time it takes to empty, but if you tilt too far, your smooth pour becomes violent glugging as bubbles forming at the bottle’s mouth block liquid from exiting.

    Researchers find that the time it takes to empty a bottle depends both on the qualities of the liquid — its viscosity and surface tension — and on the geometry of the bottle. In particular, they found that the shape of the bottle influences how quickly bubbles grow at the bottle’s mouth when tilted to the critical angle. Their findings suggest that higher tilt angles and faster pours can be achieved by optimizing bottle geometry. (Image and research credit: L. Rohilla and A. Das; via phys.org)