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Tag: Faraday waves

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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)

  • Black Hole Signature

    Black Hole Signature

    240 million years ago, pressure waves emanated from a black hole inside the Perseus Galaxy Cluster. Much later, NASA’s Chandra X-Ray Observatory intercepted those waves. Scientists raised the frequency of the signal until it fell within the range of human hearing. And then photographer John White played that sound through a petri dish of water sitting on a speaker. The result is above: a watery glimpse of a long ago black hole’s signature. Within these Faraday waves is the echo of a stellar phenomenon that took place when the very first dinosaurs walked our planet. (Image credit: J. White; via the 2023 Astronomy POTY)

  • Superradiance in Fluids

    Superradiance in Fluids

    A group of excited atoms can collectively emit more photons than they could individually in a phenomenon known as superradiance. Now researchers have shown that vibrating fluids can produce superradiance as well.

    Two different wavefields used in the experiment, each with a different distance between the circular cavities.
    Two different wave fields used in the experiment, each with a different distance between the circular cavities.

    Similar to other hydrodynamic quantum analogs, the researchers vertically vibrated a pool of liquid at a frequency that produced Faraday waves. Beneath the pool, they placed two circular wells, varying the distance between them to observe how their wave fields interacted. With a large enough vibration, the two circular wells emitted droplets (top image), and the number of droplets they produced was higher than expected for two independent wells, indicating superradiance. The results suggest that it may be possible to build even more hydrodynamic analogs of quantum systems than previously thought! (Image and research credit: V. Frumkin et al.; via APS Physics)

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    Pumping With Faraday Waves

    Vibrate a liquid pool vertically, and it will form a pattern of standing waves known as Faraday waves. Here, researchers confine those waves to a narrow ring similar in size to the wave. The confinement causes a type of secondary flow — a streaming flow — beneath the water surface. As a result, the wave pattern rotates around the ring. The applications of this rotation are pretty neat. As the team demonstrates, it can drive complex fluid networks and even create a pump! (Image and video credit: J. Guan et al.)

  • Hedgehogs Atop Waves

    Hedgehogs Atop Waves

    Since Michael Faraday, scientists have watched the curious patterns that form in a vibrating liquid. By adding floating particles to such a system, researchers have discovered spiky, hedgehog-like shapes that form near the surface. At low amplitudes, the surface patterns resemble the typical smooth rounded lobes one would expect, but as the wave amplitude increases, spikes form in the tracers, driven by the motion of the waves. (Image and research credit: H. Alarcón et al.; via APS Physics)

  • Freezing Waves

    Freezing Waves

    Vibrate a liquid, and you’ll get a pattern of standing waves known as Faraday waves. In this project, artist Linden Gledhill adds a twist to the usual view of these waves by capturing them in plastic. As the polymer liquid vibrates, Gledhill uses a flash of UV light to cure the polymer, freezing the wave pattern. Check out the original video for an even better look. (Image, video, and submission credit: L. Gledhill, 1, 2, 3, 4)

  • Shake It!

    Shake It!

    Vibrate a pool of water, and you’ll get Faraday waves, ripple-like excitations that form their own distinctive pattern compared to the driving vibration. But you don’t have to vibrate a pure liquid to see Faraday waves. A recent study observed them in vibrated earthworms!

    Odd as this may sound, the results make sense. When anesthetized (as they were in the experiments), earthworms are essentially a liquid wrapped in an elastic membrane, which is not so different from a droplet held together by surface tension.

    But why vibrate earthworms in the first place? It turns out earthworms are a good model organism for studies of vertebrate neural systems, so observing how vibrations propagate through them can provide insight into how our own nervous systems transmit information. (Image, research, and submission credit: I. Maksymov and A. Pototsky)

  • Toad Singing

    Toad Singing

    With spring heading into summer, many parts of the United States enjoy a nighttime chorus of frogs and toads. These amphibians are singing to attract mates and delineate territory. Some, like this American toad, sing from the water, and the vibration of their vocal sac creates ripples that last as long as they’re vocalizing. The toad sings by closing its nostrils and mouth, then forcing air from its lungs over its vocal cords. Those vibrations are amplified by resonance in its vocal sac, generating the high chirp we hear. (Image credit: cassiescisco)

  • Resonating on a Bounce

    Resonating on a Bounce

    When we think of resonance, we often think of it in simple terms: hit the one right note, and the wine glass will shatter. But resonance isn’t always about a one-to-one ratio between a driving frequency and the resonating system. Especially in fluid dynamics, we often see responses that occur at other, related frequencies.

    One of the simplest places to see this is with a droplet bouncing on a bath of fluid. Above you see a liquid metal droplet bouncing on a bath of the same metal. At low amplitude, the pool surface moves at the driving frequency and a droplet bounces simply upon that surface, with one bounce per oscillation. Increase the amplitude, though, and the droplet’s bounce changes. It bounces twice – one large bounce and one small bounce – in the time it takes for the pool surface to go through one cycle. This is called period doubling because the bouncing occurs at twice the driving frequency.

    Turn the amplitude up further, and the system undergoes another change. Faraday waves form on the surface. They resonate at half the driving frequency, and a droplet’s bouncing will sync up with the waves. That means the droplet returns to a one-to-one bounce with the waves, but the waves themselves are no longer reacting at the driving frequency. It’s this kind of complexity that makes fluid systems fertile grounds for studying paths toward chaos. (Image and research credit: X. Zhao et al.)

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    Psychedelic Faraday Waves

    Vibrate a pool of water and above a critical frequency, a pattern of standing waves will form on the surface. These are known as Faraday waves after Michael Faraday, who studied the phenomenon in the early half of the nineteenth century. The kaleidoscopic view of them you see here comes from photographer Linden Gledhill, who used a high-speed camera and an LED ring light reflecting off the water to capture the changing motions of the waves. The wave patterns oscillate at half the frequency of the driving vibration, and, as the driving frequency changes, the wave patterns shift dramatically. Higher frequencies create more complicated patterns. (Image and video credit: L. Gledhill)