FYFD

Tag: vibration

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    “Waves”

    The “Waves” installation by artist Daniel Palacios appears deceptively simple, just a rope mounted between two motors. But once the motors start spinning, it is anything but. The installation shifts in response to those around it, creating varying numbers of steady, standing waves or even wildly chaotic ones that whistle through the air. It’s a neat visualization of one of the most commonly-measured quantities in physics: the changes in a wave with time. (Video and image credit: D. Palacios; via Flow Vis)

  • The Tolling of the Atmosphere

    The Tolling of the Atmosphere

    Strum a musical instrument and you create a host of vibrations at many different frequencies. The same is true of our atmosphere, which rings at frequencies far too low for us to hear. The first theoretical descriptions of this atmospheric ringing date back two centuries to Pierre-Simon Laplace. A new study provides the first experimental evidence of this atmospheric ringing by analyzing 38 years’ worth of hourly atmospheric data.

    The authors found good agreement with the structures predicted by classical theory, but they point out that understanding the mechanisms that drive the ringing requires more research. Since studies of vibrations in the Earth and sun have revealed new dynamics in those systems, it’s likely analyses like these can teach us much more about how our atmosphere functions. (Image credit: NASA; research credit: T. Sakazaki and K. Hamilton; submitted by K. Hamilton)

  • 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)

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    Ejecting Water from a Smartwatch

    Making electronics water-resistant can be a challenge, but as this Slow Mo Guys video demonstrates, engineers have some clever ways to deal with unwanted liquids. The Apple Watch, for example, uses its speakers to eject water that gets into the watch during immersion. As seen above, the vibration of the speakers ejects most of the water as tiny droplets. Occasionally, surface tension makes this tough and drops instead coalesce on the watch’s surface. To counter this tendency, the speakers sometimes pause, allowing water to collect before they begin vibrating again. (Video and image credit: The Slow Mo Guys)

  • 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)

  • Measuring Contaminants in Drops and Bubbles

    Measuring Contaminants in Drops and Bubbles

    Rising bubbles and droplets are common in many chemical and industrial applications. But just a tiny concentration of contaminants on their surface can completely alter their behavior, disrupting coalescence and slowing down chemical reactions.

    Historically, it’s been hard to measure the level of contamination in these some drops and bubbles, but a new study outlines a way to measure these small concentrations by perturbing the drops and watching how they deform. By analyzing how the drop shimmies and shakes, they’re able to measure its surface tension and, ultimately, the concentration of contaminants. (Image credit: S. Sørensen; research credit: B. Lalanne et al.; via APS Physics)

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    Singing in the MRI

    We rarely consider just how complex the process is when we speak or sing. Sound waves produced in our larynx are shifted and amplified by the geometry of our throats, mouths, sinus cavities, tongues, and lips. This video provides a glimpse of that hidden complexity through a trained vocalist singing inside an MRI machine. He sings the same aria in four distinctly different vocal styles, and it’s incredible to watch all the changes his tongue, lips, and soft palette go through to produce those different sounds. (Image and video credit: T. Ross; via Flow Vis)

  • Robotic Research Facilities

    Robotic Research Facilities

    One of the major challenges in fluid dynamics is the size of the parameter spaces we have to explore. Because many problems in fluid dynamics are non-linear, making small changes in the initial set-up can result in large differences in the results. Consider, for example, a simple cylinder towed through a water tank. As the cylinder moves, vortices will form around it and shed off the back, causing the cylinder to vibrate. The details of what will happen will depend on variables like the cylinder’s size and flexibility, the speed it’s being towed at, and which directions it’s allowed to vibrate in. Mapping out the parameter space, even sparsely, could take a graduate student hundreds of experiments.

    To speed up this process, engineers are now building robotic facilities like the Intelligent Towing Tank (ITT) shown above. Like graduate students, the ITT can work into the wee hours of the night, but, unlike graduate students, it never needs to eat, sleep, or stop experimenting. Now, one could use a facility like this to brute-force the answers by testing every possible combination of parameters, but even working 24 hours a day, that would take a long time. Instead, researchers use machine learning to guide the robotic facility into choosing test parameters in a way that optimizes the factors the researchers define as important.

    Essentially, the system starts with experiments chosen at random within the parameter space, and then uses those results to select areas of interest until it’s gathered enough data to satisfy the limits specified by human researchers. In theory, a well-designed algorithm can dramatically reduce the number of experiments needed to explore a parameter space. (Image and research credit: D. Fan et al.; submitted by Kam-Yung Soh)

  • Avoiding Shear Thickening

    Avoiding Shear Thickening

    Many substances – like the cornstarch and water mixture above – exhibit a property called shear-thickening. In these fluids, deforming them quickly causes the viscosity to increase dramatically. That shear-thickening occurs when particles inside the fluid jam together, creating large chains able to resist the force being applied. That’s why the oobleck on this vibrating speaker can sustain these “cornstarch monsters”.

    Shear-thickening is useful in many contexts, but it’s problematic during manufacturing, when pumping these substances can become incredibly difficult due to the fluid’s innate resistance to flowing. A new study, though, finds that it’s possible to temporarily suppress shear-thickening using acoustic waves. The researchers used piezoelectric devices to generate acoustic waves at a frequency around 1 MHz while shearing the cornstarch mixture. The acoustic waves disrupt the formation of particle chains inside the mixture, keeping its viscosity 10 times lower than during regular shear-thickening. (Image credit: bendhoward, source; research credit: P. Sehgal et al.; submitted by Brian K.)

  • Superwalkers

    Superwalkers

    Walking droplets – drops that bounce their way across a pool of the same liquid without coalescing – have fascinated researchers in recent years with their unusual behaviors, some of which mimic quantum phenomena. In a new experiment, researchers vibrate the pool at two frequencies simultaneously, which helps support much larger droplets, known as superwalkers. When the two driving frequencies are close to a harmonic match – like at 80 Hz and just under half that at 39.5 Hz – the droplets will walk, then come to a stop, and then begin walking again. (Image and research credit: R. Valani et al.; via APS Physics; submitted by Justin B and Kam-Yung Soh)