FYFD

Search results for: “liquid jet”

  • The Sound of Bubbles

    The Sound of Bubbles

    Every day I stand in front of my refrigerator and listen to the water dispenser pouring water into my glass. The skinny, fast-moving jet of water plunges into the pool, creating a flurry of bubbles. Those bubbles come from air the water jet pulls in with it, and the sound the water makes (minus the fridge’s noises) comes from those bubbles. A short, laminar jet will make fewer bubbles and, therefore, be quieter than a a jet that falls farther before hitting the water.

    The reason? That tall jet falls for long enough that its walls start to wobble or even break up completely into separate droplets. Compared to a smooth jet, these wobbly or broken-up jets pull in more air and create more bubbles. That makes them louder. Researchers even suggest that listening to these bubbles can give a noninvasive method for finding how much fresh oxygen is in the water. (Image credit: R. Piedra; research credit: M. Boudina et al.; via APS Physics)

  • Featured Video Play Icon

    Fresh Fissures

    North of Iceland’s Fagradalsfjall, a new volcanic fissure opened in July 2023. This drone footage from Isak Finnbogason captures that fissure on its first night. Lava fountains jet from the earth, forming a complex, slow-moving river. The similarities between flowing lava and more common liquids like water never ceases to fascinate me. Even with the vast differences in temperature and viscosity, so much of their physics remains recognizably the same. (Image and video credit: I. Finnbogason; via Colossal)

  • Featured Video Play Icon

    Polymers and Fluid Sheets

    Even adding a small amount of polymers to a fluid can drastically change its behavior. Often polymer-doped fluids act more like soft solids, able to hold their shape like your toothpaste does when squeezed onto your toothpaste. Under a little stress, though, the fluids still flow; that’s why your toothpaste gets less viscous as you scrub.

    To study the changes polymers make, this research team collides two jets of fluid to create a liquid sheet. Depending on the flow rate and the added polymers, the break-up pattern of the sheet changes. By observing changes in the sheet thickness and the holes that form, they can draw conclusions about what the polymers are doing. (Video credit: C. Galvin et al.)

  • Beneath the Cavity

    Beneath the Cavity

    When a drop falls into a pool of liquid, it creates a distinctive cavity, followed by a jet. From above the surface, this process is well-studied. But this poster offers us a glimpse of what goes on beneath the surface, using particle image velocimetry. This technique follows the paths of tiny particles in the fluid to reveal how the fluid moves.

    As the cavity grows, fluid is pushed away. But the cavity’s reversal comes with a change in flow direction. The arrows now point toward the shrinking cavity — and they’re much larger, indicating a strong inward flow. It’s this convergence that creates the Worthington jet that rebounds from the surface. And, as the jet falls back, its momentum gets transferred into a vortex ring that drifts downward from the point of impact. (Image credit: R. Sharma et al.)

  • Founts of Enceladus

    Founts of Enceladus

    In its exploration of Saturn, Cassini discovered that the moon Enceladus is home to icy eruptions. Beneath its shell of ice, Enceladus has a global ocean of salty liquid water. The average thickness of the ice is 20 kilometers, putting the ocean seemingly out of reach — except at the moon’s southern pole, where icy plumes of ocean water jet out.

    Here, where the ice is thinnest, the tidal forces Enceladus experiences from Saturn and its fellow moon Dione break through the ice. As the cracks open and close, liquid from the ocean sprays out, freezing into plumes that Cassini measured. Plans are underway for new missions that prioritize further sampling of Enceladus’ ocean. For now, we can only imagine what hides in its interior ocean. (Image credit: NASA/JPL-Caltech/SSI; for more, see M. Manga and M. Rudolph)

  • Featured Video Play Icon

    Draining a Bottle

    Turn a bottle upside-down to empty it, and you’ll hear a loud glug-glug-glug as the liquid in the bottle empties and air rushes in. In this video, researchers aim a high-speed camera at the very first bubble that forms during the process. Once the bubble reaches the wider area of the bottle, it tends to pinch off in the bottle’s neck. That creates a narrow jet that pierces the bubble and flies all the way to the other side, leaving a column of liquid inside the rising bubble. Increasing the fluid’s viscosity has remarkably little effect, at least until the liquid is extremely viscous. (Image and video credit: H. Mayer et al.)

  • 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.
  • “Keeping Our Sheet Together”

    “Keeping Our Sheet Together”

    When two liquid jets collide, they form a falling liquid sheet. Here researchers explore how that sheet breaks up when the liquids involved contain polymers. The intact areas of the sheet show as dark red or almost black. The edges of the sheet appear in brighter red and yellow, outlining the holes that form and grow during breakup. The type of breakup observed depends on the concentration of polymer in the liquid. (Image credit: C. Galvin et al.)

  • Featured Video Play Icon

    Self-Stopping Leaks

    A leak can actually stop itself, as shown in this video. To demonstrate, the team used a tube pierced with a small hole. When filled, water initially shoots out the hole in a jet. The pressure driving the jet comes from the weight of the fluid sitting above the hole. As the water level drops, the pressure drops, causing the jet to sag and eventually form a rivulet that wets the side of the tube. As the water level and driving pressure continue to fall, the rivulet breaks up into discrete droplets, whose exact behavior depends on how hydrophobic the tube is. Eventually, a final droplet forms a cap over the hole and the leak stops. At this point, the flow’s driving pressure is smaller than the pressure formed by the curvature of the capping droplet. (Image and video credit: C. Tally et al.)

  • Featured Video Play Icon

    Fluid Chains

    In this video, Steve Mould tackles a question many of us have likely wondered: just why does falling water make this chain-like shape? When pouring from a slit-like orifice, water jets take on this undulating pattern. While I have no issue with Steve’s explanation of surface tension oscillations driving the shape, I’ll quibble a little bit with the idea that this hasn’t been studied. Personally, I’d connect it to the fishbone instability, which classically occurs when two jets collide. At low flow rates, though, the colliding jets form a pattern very much like this one. And if you look just past the initial conditions at the container opening, all of these flows have thicker jet-like rims colliding. I think the flows in these videos are just a slightly messier version of the low-flow-rate fishbone. What do you think? (Video and image credit: S. Mould)

More posts