FYFD

Tag: vibration

  • Scrubbing Bubbles

    Scrubbing Bubbles

    Cleaning produce helps fruits and vegetables last longer and reduces the chances for foodborne illness. But it can be a difficult feat with soft, delicate foods like tomatoes, berries, or greens. Current methods often combine ultrasonic cleaning and chemicals like chlorine. Instead, researchers are looking to boost the cleaning power of bubbles themselves by giving them an acoustic pick-me-up.

    Stop-and-go. A bubble slides along an inclined surface in a pronounced stop-and-go motion when vibrated near its frequency for translational resonance.
    Stop-and-go. A bubble slides along an inclined surface in a pronounced stop-and-go motion when vibrated near its frequency for translational resonance.

    The team combined a bubble-filled bath with sound at low (sub-cavitation) frequencies. They found that driving sound waves at the right frequency could vibrate the bubbles in a way that made them slide in a stop-and-go motion along inclined surfaces. This swaying significantly boosted their cleaning power; getting surfaces 90% cleaner than non-resonating bubbles did. (Image credit: S. Hok/Cornell University; video and research credit: Y. Lin et al.; via Gizmodo)

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    Mimicking Quantum Effects

    Over the last 15 years or so, researchers have been exploring pilot-wave theory–originally proposed by De Broglie in the 1920s as a way to understand quantum mechanics–using hydrodynamic quantum analogs. In these experiments, researchers vibrate pools of silicone oil, which allows oil drops to bounce–and in some conditions, walk–indefinitely on the pool. By mixing in obstacles that mimic classic quantum mechanical experiments, they reproduce effects like the double-slit experiment in a macroscopic system.

    In this video and the accompanying papers, a team recreates the Kapitsa-Dirac effect where a standing electromagnetic wave diffracts electrons. Here, the standing wave is instead a Faraday wave in the surface of the pool. Yet the droplets, too, diffract in a manner resembling the quantum version. (Video credit: B. Primkulov et al.; research credit: B. Primkulov et al. 1, 2)

  • Bouncing Indefinitely

    Bouncing Indefinitely

    On the surface of a gently vibrating liquid, a droplet can bounce indefinitely without coalescing, kept aloft by an air film too small to see. As long as the droplet lifts off before the air layer drains out from under it, the droplet won’t contact the water below. Now scientists have shown that this is possible with a solid surface, too.

    Using an atomically smooth mica plate, researchers were able to bounce a droplet indefinitely without wetting the surface. At higher vibration rates (below), the droplet essentially hovers in place, bouncing so quickly that we simply see its shape vibrating in response to the surface. (Image and research credit: L. Molefe et al.; via APS)

    At a high vibrational frequency, a bouncing droplet effectively hovers in space and changes its shape rather than bouncing.
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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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    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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  • “Architecture in Music”

    “Architecture in Music”

    Inside musical instruments gapes an emptiness that, to the eye of photographer Charles Brooks, resembles the vast architecture of music halls and cathedrals. In his series “Architecture in Music,” Brooks takes us into these empty spaces, revealing where the resonance at the heart of the instrument’s sound lies. In a stringed instrument like a violin, the vibration of the strings makes a relatively quiet sound on its own; it’s only in making the violin’s entire hollow body vibrate that resonance amplifies the strings. Similarly, wind instruments rely on air resonating within them to produce their sound. (Image credit: C. Brooks; via Colossal)

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    Seeing Sound

    Sound, vibration, and motion are all inextricably linked. In this BBC video, physicist Helen Czerski shows how an object’s sound and vibrations relate through the classic Chladni experiment. She vibrates a metal plate scattered with sand. At most vibration frequencies, the particles of sand bounce all over the place with no distinctive pattern. But at an object’s natural frequencies, there are standing waves and the sand gathers in spots where the standing wave has no vertical motion. The higher the vibration frequency, the more complex the pattern the sand makes. All of this plays into the sounds we hear, too. When struck, an object vibrates at many of its natural frequencies at once. That’s what gives us a rich, musical tone — all those layered frequencies. (Video and image credit: BBC)

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    Galloping Bubbles

    A buoyant bubble rises until it’s stopped by a wall. What happens, this video asks, if that wall vibrates up and down? If the vibration is large enough, the bubble loses its symmetry and starts to gallop along the wall. Using numerical simulations, the team determined the flow around the bubble. They also demonstrate several possible applications for this behavior: sorting bubbles by size, traversing mazes, and cleaning a surface. (Video and image credit: J. Guan et al.)

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    Floating in Sync

    Objects on a vibrating liquid bath can interact with each other through the waves they make as they bounce. Here, researchers look at three-armed spinners interacting in pairs and in larger groups. A pair of spinners can synchronize so that they spin together or so that they spin in opposing phases. With more spinners, more complex patterns are possible. The spinners can even “freeze” one another by forming a pattern of standing waves that keep them locked in their orientation. (Video and image credit: J. Barotta et al.; via GoSM)

  • Swarm of Surfers

    Swarm of Surfers

    Self-propelled objects can form fascinating patterns. Here, researchers investigate how small plastic “surfers” move on a vibrating fluid. Each surfer is heavier in its stern than its bow. When the fluid vibrates, the surfer creates waves that are asymmetric — deeper in the stern than at the bow. For single surfers, this imbalance propels the surfer in the direction of its bow. But with more than one surfer, other patterns form.

    The video demonstrates five of the seven patterns pairs of surfers exhibit.
    The video demonstrates five of the seven patterns pairs of surfers exhibit.

    The team looked at groups of surfers all the way up to eight members. Among pairs, the researchers found seven distinctive patterns, including orbiting groups, tailgaters, and promenading pairs. Larger groups, they found, had similar collective behaviors. They hope their surfers will be an easily accessible platform for exploring active matter. (Image and research credit: I. Ho et al.; via APS Physics)