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Search results for: “art”

  • Airflow in the Opera

    Airflow in the Opera

    Like so many other performers, the singers and musicians of New York’s Metropolitan Opera House were left without a way to safely perform when the SARS-CoV-2 pandemic began in early 2020. In search of safe ways to perform and rehearse, the Met turned to researchers at nearby Princeton University, who worked directly with the performers to explore aerosol production and airflow in the context of professional opera.

    Through visualization and other experiments, the team found that the highly-controlled breathing of opera singers actually posed a lower risk for spreading pathogens than typical speaking and breathing. Most of a singer’s voiced sounds are sustained vowels, which produce a slow, buoyant jet that remains close to a singer. The exception are consonants, which created rapid, forward-projected jets.

    In the orchestra, the researchers found that placing a mask over the bell of wind instruments like the trombone reduced the speed and spread of air. One of the highest risk instruments they found was the oboe. Playing the oboe requires a long, slow release of air, but between musical phrases, oboists rapidly exhale any remaining air from their lungs and take a fresh breath. That rapid exhale creates a fast, forceful jet of air that necessitates placing the oboist further from others. (Image credit: top – P. Chiabrando, others – P. Bourrianne et al.; research credit: P. Bourrianne et al.; via APS Physics; submitted by Kam-Yung Soh)

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    In a Box, Shaken

    Tidal areas experience lots of oscillating, back-and-forth flow that builds up patterns in the sand below. In this experiment, researchers investigate a similar situation by filling a box with water and spherical particles, then shaking the box from side-to-side. Inside the box, the particles line up in chains that are perpendicular to the direction of oscillation (think sand ripples parallel to a shoreline). In this simplified system, the team can then look at what forces align the particles, how defects in the pattern shift, and what happens when the oscillation gets bigger. (Image and video credit: T. van Overveld et al.)

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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.)

  • Why Moths Are Slow Fliers

    Why Moths Are Slow Fliers

    Hawkmoths and other insects are slow fliers compared to birds, even ones that can hover. To understand why these insects top out at 5 m/s, researchers simulated their flight from hovering to forward flight at 4 m/s. They analyzed real hawkmoths flying in wind tunnels to build their simulated insects, then studied their digital moths with computational fluid dynamics.

    During hovering flight, they found that hawkmoths generate equal amounts of lift with their upstroke and downstroke. As the moth transitions into forward flight, though, its wing orientation shifts to reduce drag, and the upstroke stops being so helpful. Instead, the upstroke generates a downward lift that the downstroke has to counter in addition to the insect’s weight. At higher forward speeds, this trend gets even worse.

    The final verdict? Hawkmoths don’t have the flexibility to twist their wings on the upstroke the way birds do to avoid that large downward lift. Since they can’t mitigate that negative lift, the insects have a slower top speed overall. (Image and research credit: S. Lionetti et al.; via APS Physics; submitted by Kam-Yung Soh)

  • Vietnam’s Emerald Isles

    Vietnam’s Emerald Isles

    Vietnam’s Hạ Long Bay is home to more than 1,600 islands, many of them made up of mountainous limestone. The area is famous for its karst features, a type of terrain formed from highly porous, water-soluble rock. Over time, water dissolves and fractures the limestone, creating karst landscapes full of caves, springs, sinkholes, and fluted rock outcroppings. The area’s erosion also produces highly fertile soil, leading to a verdant ecosystem with many unique and endemic species. (Image credit: N. Kuring/NASA/USGS; via NASA Earth Observatory)

  • Never Break the Chain

    Never Break the Chain

    Pour water out of a bottle, and you’ll see a jet with a shape that resembles chain links. Sometimes known as a “liquid chain,” this phenomenon occurs when water pours through a non-circular hole. It’s quite a complex behavior, as shown in this recent study of the nonlinear effect. Even so, the authors found that the amplitude and wavelength of the chain’s sections are tied directly to the shape of the opening. Current models of the effect don’t account for the viscosity of the liquid, though, so future experiments will have to explore how fluids other than water behave. (Image and research credit: D. Jordan et al.; via APS Physics; submitted by Kam-Yung Soh)

    A comparison of oscillating jet shapes and metal chains.
    A comparison of an oscillating jet’s shape and metal chains. Each view is rotated 45 degrees from the one before.
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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)

  • Searching for Stability

    Searching for Stability

    At present, there is no theory of relativistic fluid dynamics, which is problematic for those studying black holes, neutron star mergers, and heavy-ion collisions, where fluids may wind up moving at near-light speeds. Many current models for these systems allow energy to dissipate using equations that permit faster-than-light speeds. A new study shows that these assumptions lead to problematic results.

    The paper shows that, if the mathematical equations allow for faster-than-light speeds — thereby breaking causality — then the fluid system will behave stably to one observer and unstably to an observer in a different reference frame. In other words, there will always be a frame of reference where disturbances grow exponentially and destroy the system. That’s clearly not ideal.

    Fortunately, the paper also offers an important solution: if causality holds, the stability (or instability) of a system is the same regardless of reference frame. That’s incredibly powerful for researchers because it means that they only have to show the stability of the system in one reference frame to know that the result applies to all reference frames, so long as they’re not breaking causality. (Image credit: A. Pal; research credit: L. Gavassino; via APS Physics; submitted by Kam-Yung Soh)

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    DIY Superwalking Droplets

    Over the past few years, we’ve seen lots of research in walking droplets, especially as hydrodynamic quantum analogs. But did you know you can replicate this set-up at home and play with it yourself? This video gives an overview of the equipment you’ll need and a simple procedure to follow to get it up and running. From there, your imagination is the limit! (Image and video credit: R. Valani)

  • Fluid Flow For Digestive Health

    Fluid Flow For Digestive Health

    During digestion, our intestines use two different patterns of muscle contraction to move food through our bodies. Scientists have long wondered why we have this added complexity. Using numerical simulations of the fluid flow created by these contractions, researchers have uncovered the answer.

    Our intestines use peristalsis, a forward-with-occasional-backward flow pattern, as the main driver. The strength of the muscle contractions determines how fast the average flow speed is. When the speed is slow, our bodies have more time to absorb nutrients, but that also allows more time for bacteria to flourish on those same nutrients. The other flow pattern, segmentation, creates a weaker flow overall but with much more mixing, which again enhances nutrient uptake.

    Switching between the two patterns, the researchers found, gives the body the best of both. Segmentation can enhance mixing and provide good nutrient uptake, then peristalsis can move the contents along quickly enough that bacteria don’t have time to grow before getting flushed out. (Image credit: Kindel Media; research credit: A. Codutti et al.; via APS Physics)

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