FYFD

Tag: fluid dynamics

  • How Frogs Block Unwanted Noise

    How Frogs Block Unwanted Noise

    In a crowded room, it can be hard to pick out the one conversation you want to hear. This so-called “cocktail party problem” is one animals have to contend with, too, when a noisy landscape can obscure the calls of potential mates. American green tree frogs have a clever solution to the problem: inflating their lungs to dampen out other frog species’ calls.

    This method works because frogs have a direct anatomical connection between their lungs and their eardrums. Researchers found that when these frogs inflate their lungs, there’s a pronounced drop in their sensitivity to sound in the 1.4 – 2.2 kHz frequency band. That frequency range falls between the green tree frog’s peak mating call frequencies, but it coincides with the frequencies of other frogs living in the same regions. So rather than using their lungs to make themselves louder, these clever amphibians use them to make other frogs quieter! (Image credit: B. Gratwicke; research credit: N. Lee et al.; via Physics Today)

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    “Playing With Time”

    The Macro Room team is back with this clever video that messes with our perception of time. I’d hate to give anything away here, so just go check it out! (Image and video credit: Macro Room)

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    When Rivers Break Their Banks

    Rivers often change their course, but they do not always do so gradually. River avulsions are a bit like earthquakes — they happen suddenly and with disastrous potential. Researchers find that these sudden course changes happen when silt builds up in a river and reduces the amount of water it can carry. Eventually, the resistance to flow is large enough that the river bursts its banks in search of an easier route to the sea. That’s a deadly problem for the communities that live nearby and rely on the river’s sedimentation for their fertile farmland. But using small-scale models, scientists are beginning to unravel the physics behind avulsions, bringing hope that they can be predicted or even sustainably averted. (Video and image credit: Science)

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    Springtails Jump Off Water

    Springtails are tiny hexapods often found near water, where they execute their superpower: backflipping off the water’s surface. When standing on the water, the springtail’s hydrophilic claws protrude beneath the water surface and give it traction. But its spring-loaded furcula is hydrophobic, so when it snaps down it strikes the water without breaking through. The impact propels the springtail upward and sets it spinning at an incredible rate — Smith saw up to 290 backflips a second! (Image and video credit: Ant Lab/A. Smith)

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    When Squids Fly

    Some species of squid fly at speeds comparable to a motorboat for distances of 50 meters. The cephalopods get into the air the same way they swim underwater: by expelling a jet of water through the center of their body. Once aloft, the squids spread their tentacles to form a semi-rigid wing-like surface for lift. They can also use fins on their mantle as a canard for additional lift or control of their altitude. Researchers suspect the squids use flight as an escape mechanism to put distance between themselves and predators, but it could also be a low-energy migration strategy since a single pulse carries a squid farther in air than in water. (Video and image credit: TED-Ed)

  • The Variable Venusian Day

    The Variable Venusian Day

    Venus is a thoroughly unpleasant place thanks to its hellish temperatures and acidic clouds, but a new study adds another wrinkle to our strange sister planet: Venus’s day varies by up to 21 minutes in length. This peculiar factoid is the result of 15 years spent monitoring Venus’s rotation via radar. Previous attempts to pin down the exact length of Venus’s day produced differing answers; those disagreements make more sense in light of the new study, where individuals measurements of Venus’s rotation rate could differ by 3 minutes just from one (Earth) day to the next!

    So why does Venus’s rotation rate change so dramatically? Venus’s atmosphere is massive — 100 times more massive than Earth’s — and it spins incredibly fast. The upper layers of Venus’s atmosphere can complete a rotation in 4 Earth days, while the solid ground requires 243 Earth days. As the atmosphere spins and sloshes, some of its angular momentum gets transferred to the ground, changing the planet’s rotation rate. (Image credit: NASA/JPL-Caltech; research credit: J. Margot et al.; via AGU Eos; submitted by Kam-Yung Soh)

  • “Phoenix Rising”

    “Phoenix Rising”

    This aerial photo of Lake Owens by Paul Hoelen won a 2020 Drone Photo Award in the Abstract category. As Hoelen notes, “The phoenix rising is a symbol of re-emergence from the ashes of fire.” Lake Owens was used for years in mining and other industries, which left the lake desiccated and depleted. But nature is beginning to recover; migratory birds have returned to the lake, and life is beginning anew. (Image credit: P. Hoelen; via Colossal)

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    Flamingo Filter-Feeding

    Flamingoes are strange and ungainly creatures, but their hooked bills make much more sense when you see them eating underwater. The birds are filter feeders, and they suck water, mud, and silt in through the front of their bills and pump it back out the sides. In between hairy structures called lamellae help them separate algae, brine shrimp and other food from the mix. Be sure to turn the sound up on the video so that you can hear the sound of flamingoes at work. (Image and video credit: San Diego Zoo; via Colossal)

  • Levitating Cylinders by Lubrication

    Levitating Cylinders by Lubrication

    Here’s a surprising example of defying gravity: if you coat a vertical treadmill in oil, a cylinder held next to it will levitate! A new paper delves into the mathematics behind this surprising situation, showing that the key to keeping the cylinder aloft is the pressure that forms where the oil layer splits around the disk. For a given cylinder size and mass, there’s a unique treadmill speed that will levitate it. By experimentally testing a range of cylinder sizes and masses, the authors validated their model and showed a simply scaling argument for predicting the belt speed needed for levitation. (Image and research credit: M. Dalwadi et al.; via Nature; submitted by Kam-Yung Soh)

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    Pipe Flow and Pressure

    Whether you’re a homeowner or an engineer, at some point you’ll have to deal with pipe flow and the challenges inherent to getting water from Point A to Point B. This Practical Engineering video provides a great basic overview of pipe flow and pressure loss, whether you’re looking for an introduction to the topic or a little refresher. It’s also got some small-scale demos in an actual system to help you build intuition for what changing pipe length, diameter, and fittings does to the flow. (Video and image credit: Practical Engineering)