FYFD

Category: Phenomena

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    Flow Through Granular Beds

    We often rely on water draining through beds of grains, whether it’s the soil foundation beneath a building or the sand-and-gravel-filter used in water treatment. But how does water move through these tortuous porous passages? That’s what we see in this video, which places grains in a jig resembling an ant farm and lets us watch as water–and air–drain through the grains. The result is more complicated than you might imagine, with dry pockets, weak spots, and developing sinkholes. (Video and image credit: J. Choi et al.)

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    Inside a Bubble’s Burst

    When bubbles burst at an interface, both their exterior and interior get spread into the air. Here, researchers watch as a fog-filled bubble rises through silicone oil and settles as the surface. Instabilities ripple down the bubble’s cap as it thins, and, once the bubble bursts, the fog from within is pushed upward, curling into a vortex as it goes. (Video and image credit: R. Shabtay and I. Jacobi; via GFM)

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    Wavy Water Entry

    When an object like a sphere enters the water, it drags air into the water behind it, creating a cavity. Depending on the sphere’s impact speed, the cavity might close first under the water, forming a deep seal, or at the surface with a surface seal. But, as this video points out, water often isn’t still. Here, they explore how the sphere’s entry changes when there are ripples on the water surface. (Video and image credit: M. Ibrahim et al.; via GFM)

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    ExaWind Simulation

    Large-scale computational fluid dynamics simulations face many challenges. Among them is the need to capture both large physical scales–like those of Earth’s atmospheric boundary layer–and small scales–like those of tiny eddies moving around a wind-turbine blade. Capturing all of these scales for a problem like four wind turbines in a wind farm requires using the full computing power of every processor in a large supercomputer. That’s the level of power behind the simulation visualized in this video. The results, however, are stunning. (Video and image credit: M. da Frahan et al.)

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    Superwalking Droplets

    When placed on a vibrating oil bath, droplets have many wild behaviors, some of which mirror quantum mechanics. Even big droplets — bigger than 2 millimeters in diameter — can get in on the fun. This video shows several of these “jumbo superwalkers” in action, both singly and in groups. (Video and image credit: Y. Li and R. Valani; via GFM)

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    How the Edenville Dam Failed

    Back in May 2020, the Edenville Dam in Michigan failed dramatically, releasing flood waters that destroyed a downstream dam and caused millions of dollars of damage. In this Practical Engineering video, Grady deconstructs the accident, based on an interim report from the forensic team charged with investigating the failure. Along the way, he explains common causes of dam failures, what made the Edenville failure unusual, and how engineers build modern earthen dams to avoid this older design’s flaws. (Image and video credit: Practical Engineering)

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    Event-Based Recording

    High-speed cameras are an amazing tool in fluid dynamics, but they come with a whole host of challenges. The camera and lighting have to be positioned to deal with reflections, the data sets are enormous, and post-processing all that data takes a long time.

    Video of flow on a rotating disk.

    Here, researchers experiment instead with studying a flow using an event-based camera, which records information only when and where the brightness changes. The images and videos look strange to our eyes, but, as the authors show, they work nicely for identifying flow features and extracting valuable data. (Video and image credit: D. Sun et al.)

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    The Hydrostatic Paradox

    Engineering classes often discuss hydrostatics–the physics of non-moving water–before they cover fluid dynamics and its flows. But hydrostatics is plenty challenging on its own, as Steve Mould demonstrates in this video looking at how hydrostatic pressure depends on depth (and, not, as our intuition might suggest, on shape). As always, he has some nice countertop-scale demos to go with it. (Video and image credit: S. Mould)

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    Droplets Through a Forest

    When droplets flow through a forest of microfluidic posts, they can deform around the obstacle or break up into smaller droplets. Here, researchers explore the factors that control the outcome, as well as when droplets collide, coalesce, and mix. (Video and image credit: D. Meer et al.)

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    Leaves Dance in the Wind

    Once a breeze kicks up, leaves on a tree start dancing. Every tree’s leaves have their own shapes, some of which appear very different from other trees. But their dances have patterns, as this video shows. In it, researchers explore how leaves of different shapes deform in the wind and how they can decompose that motion to compare across leaves. (Video and image credit: K. Mulleners et al.; via GFM)

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