Tendrils of fog flow over the crest of a hill in this award-winning photograph from Ray Cao. Seen in timelapse, scenes like this show the sloshing, wave-like motion of fog. They’re a beautiful reminder that air and water move much the same. (Image credit: R. Cao/IAPOTY; via Colossal)
Tag: flow visualization
Biodegradable PIV Particles
Particle image velocimetry–PIV, for short–is used to visualize fluid flows. The technique introduces small, neutrally-buoyant particles into the flow and illuminates them with laser light. By comparing images of the illuminated particles, computer algorithms can work out the velocity (and other variables) of a flow. Typical methods use hollow glass spheres or polystyrene beads as the particles that follow the flow, but these options have many downsides. They’re expensive–as much as $200/pound–and they can potentially harm test subjects, like animals whose swimming researchers are studying. Instead, researchers are now looking at biodegradable options for PIV particles.
One study found that corn and arrowroot starches were good candidates, at least for applications using artificial seawater. The powders were close to neutrally-buoyant, had uniform particle sizes, and accurately captured the flow around an airfoil, live brine shrimp, and free-swimming moon jellyfish. (Image credit: M. Kovalets; research credit: Y. Su et al.; via Ars Technica)
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A Glimpse of the Solar Wind
In December 2024, Parker Solar Probe made its closest pass yet to our Sun. In doing so, it captured the detailed images seen here, where three coronal mass ejections — giant releases of plasma, twisted by magnetic fields — collide in the Sun’s corona. Events like these shape the solar wind and the space weather that reaches us here on Earth. The biggest events can cause beautiful auroras, but they also run the risk of breaking satellites, power grids, and other infrastructure. (Image credit: NASA/Johns Hopkins APL/Naval Research Lab; video credit: NASA Goddard; via Gizmodo)
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Espresso in Slow-Mo
Espresso has some pretty cool physics. But it’s also just lovely to watch in slow motion. This video offers a look at the making of an espresso shot at 120 frames per second (though you can also enjoy a 1000 fps version here). Watching the film form, expand, and break up at the beginning and end of the video is my favorite, but watching how the occasional solid coffee grains make their way into and down the central jet is really interesting also. (Video and image credit: YouTube/skunkay; via Open Culture)
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How Particles Affect Melting Ice
When ice melts in salt water, there’s an upward flow along the ice caused by the difference in density. But most ice in nature is not purely water. What happens when there are particles trapped in the ice? That’s the question this video asks. The answer turns out to be relatively complex, but the researchers do a nice job of stepping viewers through their logic.
Large particles tend to fall off one-by-one, which doesn’t really affect the buoyant upward flow along the ice. In contrast, smaller particles fall downward in a plume that completely overwhelms the buoyant flow. That strong downward flow makes the ice ablate even faster. (Video and image credit: S. Bootsma et al.)
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Baltic Bloom
June and July brings blooming phytoplankton to the Baltic Sea, seen here in late July 2025. On-the-water measurements show that much of this bloom was cyanobacteria, an ancient type of organism among the first to process carbon dioxide into oxygen. These organisms thrive in nutrient- and nitrogen-rich waters. Here, they mark out the tides and currents that mix the Baltic. Zoom in on the full image, and you’ll see dark, nearly-straight lines across the swirls; these are the wakes of boats. (Image credit: M. Garrison; via NASA Earth Observatory)
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Salty Swirls
Flamingos soar over swirls of salt and algae in a lake in Kenya’s Rift Valley. Shaped by winds, currents, physics, and chemistry these eddies reflect the motion of the water, evaporation patterns, and more. Without more information, it’s hard to say exactly what shapes the pattern, but it does appear reminiscent of a Kelvin-Helmholtz instability in places. (Image credit: B. Hayden/IAPOTY; via Colossal)
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Glacier Timelines
Over the past 150 years, Switzerland’s glaciers have retreated up the alpine slopes, eaten away by warming temperatures induced by industrialization. But such changes can be difficult for people to visualize, so artist Fabian Oefner set out to make these changes more comprehensible. These photographs — showing the Rhone and Trift glaciers — are the result. Oefner took the glacial extent records dating back into the 1800s and programmed them into a drone. Lit by LED, the drone flew each year’s profile over the mountainside, with Oefner capturing the path through long-exposure photography. When all the paths are combined, viewers can see the glacier’s history written on its very slopes. The effect is, fittingly, ghost-like. We see a glimpse of the glacier as it was, laid over its current remains. (Image credit: F. Oefner; video credit: Google Arts and Culture)
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A Variety of Vortices
Winds parted around the Kuril Islands and left behind a string of vortices in this satellite image from April 2025. This pattern of alternating vortices is known as a von Karman vortex street. The varying directions of the vortex streets show that winds across the islands ranged from southeasterly to southerly. Notice also that the size of the island dictates the size of the vortices. Larger islands create larger vortices, and smaller islands have smaller and more frequent vortices. (Image credit: M. Garrison; via NASA Earth Observatory)
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“Creation”
Videographer Vadim Sherbakov’s short film “Creation” is full of glittery vistas created under a macro lens. Shifting, particle-seeded flows shimmer in bright colors. Glistening deltas shift and form, and Marangoni flows generate feathers and tree-like dendritic arms. Macro flows never cease to fascinate. (Video and image credit: V. Sherbakov; via Colossal)
