FYFD

Category: Phenomena

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    Competing Time Scales

    Fluid dynamics often comes down to a competition between the different forces acting in a flow. Inertia, surface tension, viscosity, gravity, rotation — flows can be affected by all of these and more. In this video, researchers describe the three dominant forces in a rotating fluid like a planet’s atmosphere: viscosity, the fluid’s resistance to flowing; inertia, the fluid’s resistance to accelerating; and rotation, the overall spin of a fluid.

    As shown in the video, which of these three forces dominates will change depending on the speed at which the force acts. We quantify this concept using time scales; the force with the smallest time scale can act fastest and will, therefore, win the tug-of-war. (Video and image credit: UCLA SpinLab)

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  • Buccaneer Archipelago

    Buccaneer Archipelago

    Off western Australian, hundreds of low-lying islands and coral reefs jut into the ocean as part of the Buccaneer Archipelago. Tides here have a range of nearly 12 meters, so water rips through the narrow channels as the tide ebbs and flows. These fast flows lift sediment that dyes the water a bright turquoise. (Image credit: M. Garrison; via NASA Earth Observatory)

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    Why Most Wind Turbines Are 3-Bladed

    Although wind turbines can have any number of blades, most that we see have three. The reasons for that are many, as explained in this Minute Physics video. In terms of physics, wind turbines with more blades produce more torque, but they pay for it with more drag. Engineering-wise, wind turbines with odd numbers of blades have less uneven forces on them, and, thus, cost less. And, finally, people just prefer the look and sound of 3-bladed wind turbines over other forms! (Video and image credit: Minute Physics)

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  • Circulation in a Capillary Network

    Circulation in a Capillary Network

    Today’s video shows red blood cells flowing through a capillary network in a rat’s skeletal muscle. At this resolution, our eyes can follow the paths of individual red blood cells squeezing through each capillary, as well as the faster blur of thicker capillaries where many cells can pass at once. Watching videos like this is a great way to build intuition for particle image velocimetry, streaklines, and other flow visualization methods as our brains can readily recognize where the cells are moving fast and where they are slower. (Video and image credit: Dr. G. McEvoy et al.; via Colossal)

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    Protecting Wildlife from Underwater Construction

    The loud noises of construction are not just an issue for humans. Sound and pressure waves from underwater construction are a problem for water-dwellers, too. So engineers use bubble curtains around a construction site to help reduce the amount of sound that escapes. Water and air transmit sound very differently; in acoustic terms, they have very different impedance. You’ve probably experienced this yourself if you’ve ever compared the sounds of a swimming pool above and below the surface. Because some of a sound’s intensity gets lost in the water –> air –> water transition, a bubble curtain can halve the sound pressure transmitted from equipment. (Video and image credit: Practical Engineering)

  • Growing Salty

    Growing Salty

    Ngangla Ringco sits atop the Tibetan Plateau, breaking up the barren landscape with eye-catching teal and blue. This saline lake sits at an altitude of 4,700 meters, fed by rainfall, Himalayan runoff, and melting glaciers and permafrost. The lake, like many inland bodies of salt water, has no outflow. Instead, water evaporates from the lake, leaving behind any salts that were dissolved in it. Over time, those left-behind salts build up and make the lake ever saltier. (Image credit: NASA; via NASA Earth Observatory)

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    Liquefaction in Earthquakes

    In an earthquake, sand and soil particles get jostled together, forcing any water between them up toward the surface. The result is liquefaction, a state where once-solid ground starts to behave much like a liquid. Buildings can tip over and pipelines get pushed toward the surface. In this video, a geologist shows off some great demonstrations of the effect, including ones that can be easily done in a classroom with younger kids. (Video credit: California Geological Survey)

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    The Forces on an Arch Dam

    Although they’re iconic, arch dams like the Hoover Dam are relatively unusual. In this Practical Engineering video, Grady looks at the forces a dam needs to withstand and where and why an arch dam is useful. It’s a good reminder that even water that (for the most part) isn’t moving is still a challenge to deal with. (Video and image credit: Practical Engineering)

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  • Zoom Into the Sun

    Zoom Into the Sun

    Fall into our nearest star in this gorgeous high-resolution view of the Sun. Taken by Solar Orbiter, a joint NASA-ESA mission, the image stretches from the fiery photosphere — full of filaments and prominences — to the wispy yet unbelievably hot corona. It’s well worth clicking through to zoom in and around the full size image. (Image credit: ESA & NASA/Solar Orbiter/EUI Team, E. Kraaikamp; via Gizmodo)

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  • Martian Polar Spiral

    Martian Polar Spiral

    The North Pole of Mars is a raised spiral, and each winter a new layer, roughly a meter thick, of carbon dioxide ice gets deposited over it. Strong cold winds rush down from the center of the pole. Mars’s spin creates a Coriolis effect that makes the winds spiral out as they descend. When they cross a depression in the surface, it creates a vortex that erodes the depression deeper. As the depressions deepen and merge, they form the troughs seen here. For more, see this post. (Image credit: ESA/DLR/FU Berlin; NASA MGS MOLA Science Team; via APOD)