FYFD

Tag: flow visualization

  • Inside an Espresso Bed

    Inside an Espresso Bed

    When pulling a shot of espresso, there are complicated physics at play. The ground coffee is tamped into a puck-like bed of grains, through which high-temperature, high-pressure water is forced. Here, researchers used X-ray tomography to visualize how and when water moves through the bed, which affects how flavors extract.

    Composite images of water penetrating a bed of finely ground coffee (left) and a bed of coarsely ground coffee (right).
    Composite images of water penetrating a bed of finely ground coffee (left) and a bed of coarsely ground coffee (right).

    In a finely ground bed, water is relatively slow to penetrate the bed, but moves in fairly uniformly. Water can get into the coarse grind a little faster but does so less uniformly. With the new experimental technique in place, the team is interested in seeing how water temperature affects infiltration and what solids get extracted. (Image credit: top – R. Wicks, experiment – J. Foster et al.; research credit: J. Foster et al.; via Physics World)

  • Canyon Swirls

    Canyon Swirls

    For much of the year, Cañon Fiord in the Canadian Arctic lies under ice and snow, but in the summer melt season, colors peek out. Here sea ice and sediment swirl in the fjord in eddies that are kilometers wide. The sediment is largely glacial flour–rock that’s been ground into dust by glaciers. It provides critical nutrients for the marine ecosystem. (Image credit: L. Dauphin; via NASA Earth Observatory)

    Satellite image of sea ice and sediment swirling in Cañon Fiord.
  • Swirls Above the Southern Ocean

    Swirls Above the Southern Ocean

    In the Southern Ocean, obstacles are sparse. But the ice-cloaked volcano of Peter I Island is tall enough at over 1600 meters to disrupt the wind. At steady wind speeds between about 18 to 54 kilometers per hour, flowing past the island creates vortices that shed from one side and then the other. The result is a von Karman vortex street like the one seen here, flowing toward the upper right.

    The overlaid ripple structures in the cloud layer are reminiscent of gravity waves. Perhaps, the wind’s passage made some lee waves that the vortices distorted? (Image credit: M. Garrison; via NASA Earth Observatory)

    A von Karman vortex street stretches downstream from Peter I Island.
  • A Special Trio of Clouds

    A Special Trio of Clouds

    Off the coast of Alaska, March 19th, 2026 featured a trio of fascinating clouds. Southwest of Anchorage, a cyclonic polar low twisted up from cold polar air centered over warmer waters. This particular storm boasted tropical-storm-force winds and thunderstorms in its center.

    Further west, long cloud streets formed parallel to the wind as cold dry air picked up moisture from warmer polar waters. And, finally, in the bottom left of the image, alternating vortices swirl in the wake of a rocky island, forming a beautiful von Karman vortex street. (Image credit: M. Garrison/NASA Earth Observatory)

    A trio of atmospheric phenomena appear in this satellite image off Alaska: a polar low, cloud streets, and a von Karman vortex street.

  • Shocked Jets

    Shocked Jets

    Breaking a jet of liquid into droplets lies at the heart of many industrial processes: spray painting, fuel injection, and asthma inhalers, to name a few. Here, researchers are looking at a different method of breaking up a liquid jet: shooting a shock wave along its length. The poster shows five different snapshots of the jet’s response. There are, variously, mists of fine droplets, wavy distortions of the jet, sheets, ligaments, and droplets of many sizes. (Image credit: S. Rao et al.)

    Research poster showing black and white images of liquid jets after a shockwave passed along the length of each jet.
    Research poster showing black and white images of liquid jets after a shock wave passed along the length of each jet.
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    Drying Out Microbe-Filled Droplets

    Ocean sprays, coughs, and sneezes are just a few of the ways that droplets full of bacteria and salt can get aloft on a breeze. How do these bacteria stay viable even as their droplet evaporates? That’s the question behind this video’s research.

    When a bacteria-laden droplet or a salt-laden droplet dries, the evaporating droplet’s contact area shrinks, leaving behind only a concentrated lump of bacteria or salt. But when droplets contain both salt and bacteria, the drying droplet’s contact line gets pinned, leaving a larger area stain. The bacteria’s presence seems to promote crystallization of the salt, which–in turn–traps water in isolated spaces, perhaps helping the bacteria stay viable longer. (Video and image credit: R. Ran et al.)

    Animation of three droplets drying out. When all three components–water, salt, and bacteria–are in a droplet, the drying process looks very different.
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    Soaring Over Icelandic Lava Fields

    We’re terribly spoiled these days when it comes to footage of lava and volcanic eruptions. Back when I started FYFD, I could find very few decent photos of lava flows to illustrate posts. And now, thanks to drone cameras, we have a glut of absolutely gorgeous footage of flowing lava. This particular example comes from photographer Jan Erik Waider, who specializes in the ice, fire, and flows of northern landscapes.

    Waider’s lens offers us a detailed, almost abstract view of these rivers of lava. I especially enjoy his shots looking directly down on lava. Watching the cooled rock rafting along on the lava is like seeing a fiery version of sea ice floes. (Video and image credit: J. Waider; via Laughing Squid)

  • Herring Spawn

    Herring Spawn

    From mid-February to early May, tiny silvery Pacific herring gather along the shallow coastlines of Vancouver Island off British Columbia, Canada. In these sheltered waters, they spawn; female fish produce sticky eggs and males flood the area with milt, which turns the water a milky turquoise or green. The colors can be so vivid that the spawn is visible to satellites.

    Barkley Sound, on the island’s southwestern side, frequently hosts spawning, as its rocky shoreline provides protection and the pockets of lower salinity that the fish favor. After spawning, the fish migrate back to their feeding grounds in deeper, nutrient-rich waters. (Image credit: R. Cutler; via NASA Earth Observatory)

    A herring spawn clouding the waters along Vancouver Island on February 16, 2026.
    A herring spawn clouding the waters along Vancouver Island on February 16, 2026.
    A herring spawn event near Forbes Island in Barkley Sound turns the shoreline green.
    A herring spawn event near Forbes Island in Barkley Sound turns the shoreline green.
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  • Supersonic Jet Interaction

    Supersonic Jet Interaction

    When supersonic jets get emitted into rarefied air, they behave differently than they do in regular atmospheric conditions. Here, researchers picture three different configurations these jets can take. In the top image, the jets are close enough together that they appear to merge into a narrow supersonic jet. In the middle image, the jets are not quite as close together. They merge but form what appears to be a subsonic wake. In the final image, the jets are far enough apart that they don’t merge, although they do appear to “lean in” toward one another. (Image credit: S. Lee et al.)

    Research poster showing two supersonic jets interacting in a rarefied atmosphere.
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    Seeing Stress in an Avalanche

    Researchers sometimes study avalanches and other granular flows in a rolling drum, where grains can cascade down continuously. Here, the twist is that they’ve done it with photoelastic disks, which show stress patterns when viewed under crossed polarizing filters.

    In any given moment, the contacts between neighboring particles form a force chain that lights up the disks. In motion, the effect resembles lightning forking and branching across the sky. The close-ups of stress reverberating during impact are especially mesmerizing. (Video and image credit: R. Hodgson et al.)

    Animation of stress reverberating through particles as they roll in a drum.
    Animation of stress reverberating through particles as they roll in a drum.
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