The colorful coastline of the Bazaruto Archipelago extends off East Africa. Regions of shallow waters, seagrass meadows, and coral reefs appear in shades of tan, green, and turquoise. Deeper waters appear blue. The coastlines, deltas, and tidal flats are shaped by moderate tides that rise and fall a few meters each day; strong currents run in the channels between islands, carving and reshaping the sediment. (Image credit: W. Liang; via NASA Earth Observatory)
Tag: fluid dynamics
“The Haboob”
Haboobs are a dust storm driven by the strong winds at the forefront of weather fronts and thunderstorms. Those powerful winds pick up dust in arid and semi-arid landscapes, creating billowing, turbulent clouds that appear downright apocalyptic.
This particular haboob formed in Arizona in August 2025 and was caught in timelapse by photographer and storm chaser Mike Olbinski. The visuals–as always–are incredible. Definitely watch to the very end, as the haboob advances on the runway at Sky Harbor Airport. The tension is palpable as you watch flights line up and try to make it off the ground before the haboob swallows them. (Video and image credit: M. Olbinski)
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Thunderstorms Make Trees Glow
Scientists have long hypothesized that the high electrical charge of thunderstorms could produce an opposite charge in the ground that would discharge from the forest canopy. But this phenomenon, known as a corona, had never been observed on actual trees. A new study, however, has observed this ghostly ultraviolet (UV) glow from the tips of sweetgum leaves and loblolly pine needles during thunderstorms.
Catching these coronae in action required a new kind of UV detector that was ultra-sensitive to the particular band of UV-light emitted by coronas, hot fires, or mercury lamps. Since the latter two weren’t present during the team’s field observations, they were able to conclude that the light they detected came from coronae.
The group observed that corona discharges were transient, jumping from leaf to leaf and branch to branch across the forest canopy. For any creature capable of detecting that glow by eye, it must be incredible to watch the treetops lit by their own ever-shifting auroras during every thunderstorm. (Image credit: W. Brune; research credit: P. McFarland et al.; via SciAm)
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Making Sound Visible
Sound is not something we can typically see, though there are ways to visualize it, including cymatics and special acoustic cameras. This video pursues a different tactic: using schlieren photography and stroboscopic lighting to show how sound waves reflect and deflect. It’s no easy feat, but one worth enjoying–especially when others have already done the hard part for you! (Video and image credit: All Things Physics; submitted by David J.)
Aging Salty Ice
When ice forms in salty water, it starts out mushy and porous. Salt does not freeze neatly into ice’s crystalline structure, so the forming ice has pores and gaps where salty brine gathers. As the ice ages, more brine is pushed out and gradually convects downward, due to its greater density. Over time, this makes the ice layer thinner but more solid, with fewer pores. You can see a timelapse of the process in a laboratory experiment below. (Image credit: sea ice – C. Matias, experiment – F. Wang et al.; research credit: F. Wang et al.)
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Mixing Bubble Caps
When bubbles form atop the ocean or in our cups, they typically live short lives. Although the bubble can exchange fluid with the pool below, this only happens at the foot of the bubble cap. There, thinner patches form and, due to their buoyancy, rise up along the bubble’s surface. Over time, these lighter, thinner patches reduce the amount of fluid in the cap–causing the bubble to thin and eventually burst.
Here, researchers show that thinning–visible in the dark blue plumes rising up the bubble cap–when there’s no turbulence in the surrounding air. But as turbulence outside the bubble increases, the thinner patches stretch and deform across the cap. In the image series, turbulence increases moving from top to bottom. (Image credit: T. Aurégan and L. Deike)
“Arctic Fox in Blizzard”
A blue arctic fox bears the wind and snow of a Norwegian blizzard in this image by photographer Klaus Hellmich. The wind is strong enough to move snowflakes several centimeters in the time the camera’s shutter is open. This leaves the image full of streaklines that reveal the paths taken by the wind and snow. This visualization technique is useful in the lab, too. (Image credit: K. Hellmich; via Colossal)
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Richtmyer-Meshkov Instability
If you send a shock wave through a magnetized plasma–something that happens in both supernova explosions and inertial confinement fusion–it can trigger an instability known as the Richtmyer-Meshkov instability. The image above shows a form of this, taken from a simulation. Rather than treating the plasma as a single idealized fluid, the researchers represented it as two fluids: an ion fluid and an electron fluid. This allowed them to better capture what happens when certain components of the plasma react to changes faster than others do.
The image itself shows the electron number density across the fluid, where darker colors represent higher electron number density. The interface between high and low-densities shows a roll-up instability that resembles the Kelvin-Helmholtz instability, but there are also regions of mushroom-like plumes that more closely resemble Rayleigh-Taylor instabilities.
The authors note that these structures don’t appear in simulations that represent a plasma as a single fluid; you need the two-fluid representation to see them. (Image and research credit: O. Thompson et al.)
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Testing Structures Against Hurricane Storm Surge
When hurricanes hit coasts, they bring with them incredible storm surge, which puts buildings right in the middle of ocean waves. To understand how to better protect against those conditions, engineers use facilities like the Directional Wave Basin to create smaller-scale versions of hurricanes. In this Practical Engineering video, Grady visited during a test that compared two identical one-third-scale houses subjected to the same storm conditions–except that one house had an additional foot (3ft at real-scale) of elevation. The results are pretty spectacular.
This isn’t a short video, but it’s well-worth a watch. I think Grady does a great job of explaining why engineers need (admittedly) expensive facilities like this one to help guide both engineering and regulatory decisions. (Video and image credit: Practical Engineering)
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Improving Turbulence Models
Calculating turbulent flows like those found in the ocean and atmosphere is extremely expensive computationally. That’s why forecasting models use techniques like Large Eddy Simulation (LES), where large physical scales are calculated according to the governing physical equations while smaller scales are approximated with mathematical models. Researchers are always looking for ways to improve these models–making them more physically accurate, easier to compute, and more computationally stable.
In a new study, researchers used an equation-discovery tool to find new improvements to these models for the smaller turbulent scales. They started by doing a full, computationally expensive calculation of the turbulent flow. The equation-discovery tool then analyzed these results, looking to match them to a library of over 900 possible equations. When it found a form that fit the data, the researchers were then able to show analytically how to derive that equation from the underlying physics. The result is a new equation that models these smaller scales in a way that’s physically accurate and computationally stable, offering possibilities for better LES. (Image credit: CasSa Paintings; research credit: K. Jakhar et al.; via APS)
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