FYFD

Tag: biology

  • Undulating Keeps Flying Snakes Steady

    Undulating Keeps Flying Snakes Steady

    Flying snakes undulate through the air as they glide. But, unlike on land, these wiggles aren’t for propulsion. A new study shows instead that they are key to the snake staying stable in flight.

    Upon take-off, a flying snake flattens its body, forming a wing-like shape that helps them generate lift and control drag. But while they glide, they also slither and pitch their tail.

    Researchers recorded more than 150 flights by live snakes, then used that data to construct their own digital snake. The model could fly like a real snake or be tested without undulations to see what would happen. The researchers discovered that, without that mid-air slithering, the snake quickly lost control and rolled to the side. (Image and research credit: I. Yeaton et al.; via NYTimes; submitted by Kam-Yung Soh)

  • Quantifying Bioluminescence

    Quantifying Bioluminescence

    Some single-celled organisms, like dinoflagellates, light up when disturbed. This bioluminescence is considered a defense mechanism, triggered by threats to the organism. Now researchers are quantifying just what it takes to light up a single dinoflagellate.

    Dinoflagellates respond both to stress caused by the fluid flow around them and to mechanical deformation — in other words, getting poked. Both methods involve bending and stretching the dinoflagellate’s cell wall, which stretches calcium-ion channels connected to bioluminescence. The researchers found that the intensity of the light produced depended both on the amount and speed of cell wall deformation.

    The model built from their observations should help scientists better understand what forces cause a specific response. That means dinoflagellates could be used as a non-invasive means of understanding fluid flow around swimmers like dolphins or sea lions! (Image and research credit: M. Jalaal et al.; via APS Physics)

  • The Challenges of Being Small

    The Challenges of Being Small

    For juvenile fish, feeding is a challenge. Their small size — often less than 5 mm in length — makes hydrodynamically capturing prey much harder because of viscosity’s relatively larger effect on them. But size may not be the only factor in determining their success, as a new study shows.

    Researchers studied feeding behaviors of two, equally-sized species’ larvae: zebrafish and guppies. The biggest difference between these two species is their developmental time prior to beginning to hunt on their own. Guppies develop five times longer than zebrafish larvae before they start feeding.

    Both fish have the same hydrodynamic limitations to overcome. If you look closely at the first image, you’ll see fluid being pushed ahead of the fish as it swims. The researchers refer to this as a bow wave, and it effectively announces to any prey that the fish is approaching. To sneak up on prey, the fish has to be able to generate enough suction force to pull its food in from beyond the bow wave’s reach. The experiments showed that guppies were able to do this reliably, while zebrafish could not. The subsequent difference in their feeding success was stark: the guppies’ success rate was almost five times that of the zebrafish! (Image and research credit: T. Dial and G. Lauder, source; via G. Lauder)

  • Shake It!

    Shake It!

    Vibrate a pool of water, and you’ll get Faraday waves, ripple-like excitations that form their own distinctive pattern compared to the driving vibration. But you don’t have to vibrate a pure liquid to see Faraday waves. A recent study observed them in vibrated earthworms!

    Odd as this may sound, the results make sense. When anesthetized (as they were in the experiments), earthworms are essentially a liquid wrapped in an elastic membrane, which is not so different from a droplet held together by surface tension.

    But why vibrate earthworms in the first place? It turns out earthworms are a good model organism for studies of vertebrate neural systems, so observing how vibrations propagate through them can provide insight into how our own nervous systems transmit information. (Image, research, and submission credit: I. Maksymov and A. Pototsky)

  • Featured Video Play Icon

    How Animals Stay Dry in the Rain

    Getting wet can be a problem for many animals. A wet insect could quickly become too heavy to fly, and a wet bird can struggle to stay warm. But these animals have a secret weapon: tiny, multi-scale roughness on their wings, scales, and feathers that helps them shed water. Watch the latest FYFD video to learn how! (Image and video credit: N. Sharp; research credit: S. Kim et al.)

  • 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.)

  • 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)

  • Featured Video Play Icon

    How COVID-19 Affects the Lungs

    One of the best known COVID-19 symptoms of this pandemic is difficulty breathing, and while you’ve likely heard a lot about ventilators used to help patients get oxygen, you may not know much about the processes that cause the breathing problems. This video from Deep Look provides a solid overview of the infection route and how lung damage occurs during infection. Perhaps unsurprisingly — this is FYFD, after all — fluid dynamics plays a major role in this process, both under normal conditions and when air sacs in the lungs get damaged by the body’s immune system responding to the virus. (Image and video credit: Deep Look)

  • Featured Video Play Icon

    Singing in the MRI

    We rarely consider just how complex the process is when we speak or sing. Sound waves produced in our larynx are shifted and amplified by the geometry of our throats, mouths, sinus cavities, tongues, and lips. This video provides a glimpse of that hidden complexity through a trained vocalist singing inside an MRI machine. He sings the same aria in four distinctly different vocal styles, and it’s incredible to watch all the changes his tongue, lips, and soft palette go through to produce those different sounds. (Image and video credit: T. Ross; via Flow Vis)

  • Bristling Sharkskin Fights Separation

    Bristling Sharkskin Fights Separation

    The speedy shortfin mako shark has a secret weapon to fight drag: bristling denticles that line its fins and tail. Denticles are tiny, anvil-shaped enamel scales on the mako’s skin. In the photo above, each one is about 100 microns across. Under normal conditions, with flow moving over the shark from nose to tail, the denticles lie flat, providing no interference.

    But when sudden changes in flow near the shark’s skin cause water to begin moving in the opposite direction, the denticles flare up. Their rise interferes with the reversed flow, trapping it in small eddies beneath each denticle. Since that flow reversal is a precursor to the flow separating from the shark’s body, the bristling effectively cuts off flow separation before it can begin. The result is much less separation and much lower drag. Once the flow stops trying to move upstream, the denticles settle back into their original place. (Image credit: mako shark – jidanchaomian, denticles – J. Oeffner and G. Lauder, illustration – A. Lang, bristling – A. Lang et al.; research credit: A. Lang and A. Lang et al.; submitted by Kam-Yung Soh)