![Black and white image of a film pulled outward and breaking into droplets. Text reads, "The [0.05%] surfactant renders the ejected droplets prone to 'popping'."](https://fyfluiddynamics.com/wp-content/uploads/surfburst2.png "Black and white image of a film pulled outward and breaking into droplets. Text reads, \"The [0.05%] surfactant renders the ejected droplets prone to 'popping'.\"")
![Black and white image of a film pulled outward and spreading in unevenly. Text reads, "When surfactant concentration is further increased [to 1%], drop spreading resumes."](https://fyfluiddynamics.com/wp-content/uploads/surfburst3.png "Black and white image of a film pulled outward and spreading in unevenly. Text reads, \"When surfactant concentration is further increased [to 1%], drop spreading resumes.\"")
A few years ago, researchers described how an alcohol-water droplet atop an oil bath could pull itself apart through surface tension forces. Dubbed Marangoni bursting, this phenomena has shown up several times since. Here, researchers explore a twist on the behavior by adding surfactants to see how they affect the bursting phenomenon. (Video and image credit: K. Wu and H. Stone; via GFM)
With a depth of nearly 600 meters, Crater Lake in Oregon is the deepest lake in the United States. It’s known for its brilliant blue hue and startling clarity. But, like other deep lakes, Crater Lake is changing as temperatures warm. It’s edging ever closer to a day where its deep, cold waters no longer mix.
Although the details of mixing vary from lake to lake, older records show that most deep lakes would overturn and fully mix on a frequency that ranged from twice a year to every seven years. This overturning happens when winds push frigid, near-frozen water. As that water approaches the shoreline, it gets forced downward, where the pressure at depth makes the cold water denser still, causing it to sink beneath the warmer water layer near the lake bottom. That kicks off larger-scale mixing that redistributes oxygen, nutrients, and toxins in the lake.
When this regular mixing stops, the entire ecosystem gets affected. Over time, oxygen gets depleted in deeper in the lake, leaving a dead zone unable to support fish and other aquatic life. Meanwhile, longer and warmer growing seasons favor phytoplankton and algae that cloud the waters and disrupt a lake’s unique ecology.
For a much more detailed look at deep lake mixing and the changes we’re seeing, check out this article over at Quanta Magazine. It’s a longer read but well worth your time. (Image credit: N. Perez Aguilar; see also: Quanta Magazine)
Adding just a little polymer to a pipe flow speeds it up by reducing drag near the wall. But the effects on turbulence away from the wall have been harder to suss out. A new experiment shows that added polymers suppress eddy formation in the flow and reduce how much energy is lost to friction and, ultimately, heat. In particular, the researchers found that polymer stress helped stabilize shear layers in the flow and prevent them from destabilizing into more turbulent flow. (Image credit: S. Wilkinson; research credit: Y. Zhang et al.; via APS)
Instruments aboard NASA’s PACE mission are able to distinguish far more about phytoplankton blooms than previous satellites. This image shows chlorophyll concentrations in the Norwegian Sea in July 2025. Chlorophyll acts as a proxy for phytoplankton, which produce the chemical as they process sunlight into food and oxygen.
Despite their microscopic size, phytoplankton have enormous collective effects. Scientists estimate that phytoplankton produce as much as half of the Earth’s oxygen in addition to helping transport carbon dioxide from the atmosphere into the deep ocean. They are also the foundation of the marine food web, feeding nearly all life in the ocean. (Image credit: W. Liang; via NASA Earth Observatory)
As humanity pumps carbon dioxide into the atmosphere, the ocean absorbs about a quarter of it. This exchange happens largely through bubbles created by breaking waves. When waves grow large enough to break, their crests curl over and crash down, trapping air beneath them. The turbulence of the upper ocean can push these buoyant bubbles meters under the surface, where the gases inside them dissolve into the surrounding water. This is how the ocean gets the oxygen used by marine animals, but it’s also how it gathers up carbon dioxide.
Current climate models often approximate this process using only the wind speed, but a recent study took matters a step further by modeling wave breaking and bubble generation, too. While they found a global carbon uptake that was similar to existing models, the researchers found their breaking wave model showed more variability in where carbon gets stored. For example, more carbon got absorbed in the southern hemisphere, where oceans are consistently rougher, than in the northern hemisphere, where large landmasses shelter the oceans. (Image credit: J. Kernwein; research credit: P. Rustogi et al.; via Eos)
Shades of blue, green, and purple light the Icelandic sky in this image from December 2023. Incoming solar wind particles hit oxygen and nitrogen atoms high in the atmosphere, exciting their electrons and creating this distinctive glow. We’re currently near the peak of our Sun’s 11-year solar cycle, meaning that high numbers of sunspots and outbursts will continue, likely giving us more stunning auroras like this one. (Image credit: J. Zhang; via APOD)
P.S. – This post–this one right here–is FYFD’s 4000th post! When I started this blog back in 2010 as a graduate student, I never imagined that I would have so much to write about the physics of fluids. But this subject is one that just keeps on giving, so I keep on writing. Thanks for joining the fun! – Nicole
Fresh snow shines white on the southern end of Greenland in this satellite image, taken in late February 2025. Whorls of sea ice sit off the coast, where they trace out patterns that reflect the winds and ocean currents of the region. Arctic sea ice typically reaches its largest extent by early March before experiencing a long season of melting. Both the presence and absence of sea ice have a large effect on the Arctic regions. Sea ice helps dampen wave activity; without it, seas are higher and more dynamic, creating more aerosols that seed cloud cover in the Arctic and elsewhere. (Image credit: L. Dauphin; via NASA Earth Observatory)
Photographer Ernie Button explores the stains left behind when various liquors evaporate. This one comes from a single malt scotch whisky by The Balvenie. The stain itself is made up of particles left behind when the alcohol and water in the whisky evaporate. The pattern itself depends on a careful interplay between surface tension, evaporation, pinning forces, and internal convection as the whisky puddle dries out. (Image credit: E. Button/CUPOTY; via Colossal)
Taking a deep breath may actually help you breathe easier, according to a new study. When we inhale, air fills our alveoli–tiny balloon-like compartments within our lungs. To make alveoli easier to open, they’re coated in a surfactant chemical produced by our lungs. Just as soap’s surfactant molecules squeezing between water molecules lowers the interface’s surface tension, our lung surfactants gather at the interface and lower the surface tension, making alveoli easier to inflate.
But things are a little more complicated in our lungs than in our kitchen sink because of our constant cycle of breathing, which stretches and compresses our lungs’ surfaces and surfactant layers. Imagine a flat interface, lined with surfactant molecules; then stretch it. As the interface stretches, gaps open between the surfactant molecules and allowing molecules from the interior of the liquid to push their way to the newly stretched interface, changing the surface tension. If the interface gets compressed, some of the excess molecules will get pushed back into the liquid bulk.
In looking at how lung surfactants respond to these cycles of compression and stretching, the researchers found that the lung liquid develops a microstructure during cycles of shallow breathing that makes the surface tension higher, thus making lungs harder to fill. In contrast, a deep breath like a sigh replenished the saturated lipids at the interface, lowering surface tension and making lungs more compliant. So a deep sigh actually can help you breathe easier. (Image credit: F. Møller; research credit: M.. Novaes-Silva et al.; via Gizmodo)
P.S. — I’ve got a book (chapter)! Several years ago, I joined an amazing group of women to write two books (one for middle grades and one for older audiences) about our journeys as scientists. And they are out now! In fact, today we’re holding a “Book Bomb” where we aim for as many of us as possible to buy the book(s) on the same day. If you’d like to join (and get ahead on your gift shopping), here are (affiliate) links:
Winds from the north made for wild conditions at Nazaré in Portugal. Photographer Ben Thouard caught these crashing waves in the late afternoon, when the low sun angle illuminated the spray of the surf. Every year teratons of salt and biomass move from the ocean to the atmosphere, much of it through turbulent wave action driven by the wind. Here, the wind rips droplets off of wave crests, but smaller droplets reach the atmosphere when bubbles–trapped underwater by crashing waves–reach the surface and burst. (Image credit: B. Thouard/OPOTY; via Colossal)
