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Search results for: “vortex”

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    Spinning Liquids With Lego

    One way to explore the effects of spinning liquids at high-speeds is to build an expensive and precise lab apparatus. Another method is to raid the Lego bin. Here, a YouTuber builds ever-more-elaborate Lego constructions to spin a sphere of water. He begins with a relatively straightforward magnetic stirrer that creates a bathtub vortex in his sphere, but as the set-up grows, he eventually encases the sphere to spin the entire thing at high-speed. It’s a cool way to see how spinning liquids react, from forming a vortex to spin coating the interior of the sphere and to generating a parabolic interface between air and liquid. Set-ups like these are not merely for fun, though; scientists use them to simulate the interiors of planets. (Image and video credit: Brick Technology; submitted by clogwog)

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    Walking in the Wake

    Flow visualization is an important tool in fluid dynamics, and scientists have many ways to capture and visualize flow information. But our methods are not the only — or even the best — ways to express a flow. Here, engineers teamed up with architects and artists to explore the flow behind an oscillating cylinder. When free to move forward-and-backward the cylinder’s wake takes on three distinctively forms. The team explored many ways to display the wakes — drawings, 3D-printed sculptures, and more — before ultimately building an art installation that lets visitors walk through the wake to experience it. I love the creativity of these interdisciplinary efforts. To see a similar, yet very different, take on the wake of a cylinder, check out this interpretative dance. (Image and video credit: P. Boersma et al.)

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    A Fractal Raft From a Spinning Top

    File this one under Cool Things I Would Have Never Thought Of. In this video, researchers play around with the flow around a spinning top and end up creating a fractal, granular raft. By immersing a top in dyed fluid, they show the toroidal vortices that form around the spinning toy. Then, instead of dye, they add a stretchy elastomer compound that cures over time. The elastomer stretches into thin ligaments in the swirling flow around the top. Eventually, it breaks apart into spherical drops of all different sizes.

    Once the top is removed, the elastomer drops slowly float to the surface. Surface tension and the Cheerios effect draw the drops together, and because of their many sizes, the rafts that form are fractal. (Image and video credit: B. Keshavarz and M. Geri)

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    “Reconfiguring It Out”

    Leaves flutter and bend in the breeze, changing their shape in response to the flow. Here, researchers investigate this behavior using flexible disks pulled through water. The more flexible the disk and the faster the flow, the more cup-like the disk’s final shape. Adding tracer particles to the water allows them to visualize the flow behind the disk. Every disk leaves a donut-shaped vortex ring spinning in its wake, but the more reconfigured the disk, the narrower the vortex. This, ultimately, reduces drag on the disk. That’s why trees in heavy winds streamline their branches and leaves; that flexibility lowers the drag the tree’s roots have to anchor against. (Image and video credit: M. Baskaran et al.)

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    Dolphins Playing With Bubble Rings

    Blow a jet of air underwater and you can make a bubble ring. It takes some practice for humans, or you can use a device. In this video, a team introduced wild dolphins to a bubble-ring-making machine and observed how the dolphins reacted. After some initial wariness, the animals played with them for hours, creating games and having fun. Note that there are some dolphins who create their own bubble rings to play with, so it’s hard to say that these particular dolphins have never seen a bubble ring before. But even if they have seen the bubbles, they wouldn’t have seen a machine making them. (Image and video credit: BBC Earth)

  • Actinoform Clouds

    Actinoform Clouds

    Flower-shaped actinoform clouds, like those seen on the left side of this satellite image, were only discovered in the 1960s once satellite imagery allowed meteorologists to identify cloud structures that were too large to recognize from the ground. Often appearing over the ocean, these clouds can stretch over hundreds of kilometers, bringing drizzling rain.

    This particular set of actinoform clouds have some distinctive neighbors in the right side of the image, where V-shaped slashes through the cloud cover mark the origins of two von Karman vortex streets. The vortex streets appear downwind of two rocky islands, Alejandro Selkirk Island and Robinson Crusoe Island. (Image credit: L. Dauphin; via NASA Earth Observatory)

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    Meet BILLY

    Many wings in nature are not rigid. Instead they flex and curve with the flow. Here researchers imitate that phenomenon with BILLY (Bio-Inspired Lightweight and Limber wing prototYpe). Using an evolutionary-style algorithm, BILLY determines its own optimal flapping characteristics to maximize performance. Its flexible membrane-style wing actually performs better than a rigid wing! Check out the end of the video for some flow visualization of the leading edge vortex. (Image and video credit: A. Gehrke et al.)

  • Spinning Off-Axis

    Spinning Off-Axis

    To make a vortex in the laboratory, researchers typically set a tank on a rotating platform and allow the water to drain out a hole in the center of the tank. In that case, a vortex forms over the drain (like in your bathtub!) and remains centered over the hole. In nature, though, vortices rarely follow such a simple path.

    In this experiment, researchers moved the drainage hole so that it is not aligned with the tank’s axis of rotation. Although the vortex forms over the drain (marked by a yellow dot in the lower image), it quickly moves away, following a roughly circular path around the axis until it comes to a stop. Green dye marks fluid from the tank’s bottom boundary layer, which eventually gets entrained up into the vortex. (Image and research credit: R. Munro and M. Foster; via Physics Today)

    Timelapse animation showing the development of the vortex. The yellow dot marks the location of the drain.
    Timelapse animation showing the development of the vortex. The yellow dot marks the location of the drain.

  • Tidal Vortices

    Tidal Vortices

    Local topography in the Sea of Okhotsk funnels water to create some of the largest diurnal tides in the world — nearly 14 meters! The currents rushing past islands and outcrops create swirling vortices like the ones seen in this natural-color satellite image. In some places, you can even see multiple vortices, strung together into a von Karman vortex street. At high tide, the vortex streets stretch westward, but at low tide they point east. (Image credit: N. Kuring/NASA/USGS; via NASA Earth Observatory)

  • Perching Aerodynamics

    Perching Aerodynamics

    When birds come in for a landing, they pitch back and heave their wings as they come to a stop in a perching maneuver. Some birds, researchers noticed, partially fold their wings during the move, creating what’s known as a swept wing. Curious as to the effect of this sweep, the team recreated the wing motion of a perching bird using two flat plates — one rectangular and one swept — and measured the flow around them during the maneuver. They found that the swept wing had greater lift, thanks to a spanwise flow inherent to swept wings that helped stabilize the leading-edge vortex. (Image credit: D. George; research credit: D. Adhikari et al.; via APS Physics)

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