When bubbles burst at an interface, both their exterior and interior get spread into the air. Here, researchers watch as a fog-filled bubble rises through silicone oil and settles as the surface. Instabilities ripple down the bubble’s cap as it thins, and, once the bubble bursts, the fog from within is pushed upward, curling into a vortex as it goes. (Video and image credit: R. Shabtay and I. Jacobi; via GFM)
Glacier-fed rivers are often rich in colorful sediments. Here, photographer Jan Erik Waider shows us Iceland’s glacial rivers flowing primarily in shades of blue. While the wave action and diffraction in these videos is great, the real star is the turbulent mixing where turbid and clearer waters meet. Watch those boundaries, and you’ll see shear from flows moving at different speeds which feeds the ragged, Kelvin-Helmholtz-unstable edge between colors. (Video and image credit: J. Waider; via Laughing Squid)
When a fluid coats the inner walls of a cylinder, it can move downward in what’s called a collar flow. In our airways, a sinking collar flow can thicken as it falls, eventually blocking the airway completely.
In a Newtonian fluid, this thickening during motion is essentially unavoidable; any small disturbance to the fluid will make its thickness change. But in a viscoplastic fluid–one more akin to the mucus in our airways–researchers found that, below a critical film thickness, the collar flow won’t thicken to form a blockage. (Image and research credit: J. Shemilt et al.; via APS)
![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)
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)
Stars about eight times more massive than our sun end their lives in supernovas, incredible explosions that rip the star apart. The earliest stages of this explosion are something we’ve never observed firsthand, until now. A new study reports observations of the supernovaΒ explosionΒ SNΒ 2024ggi, detected here on Earth on 10 April 2024. Only 26 hours later, researchers pointed the Very Large Telescope at it, capture data that revealed its oblong shape as the initial explosion reached the star’s surface.
What you see above and below are not the actual supernova. They are an artist’s conception of the event, based on the researchers’ observation data. That data is enough to rule out several existing supernova models and will no doubt guide new models of star death going forward. (Image credit: ESO/L. CalΓ§ada; research credit: Y. Yang et al.; via Gizmodo)
The Rayleigh-Taylor instability–typically marked by mushroom-shaped plumes–occurs when a dense fluid accelerates into a less dense one. But researchers have now demonstrated the effect at quantum scales, too.
For their experiment, the group used a Bose-Einstein condensate of sodium atoms and made the interface between them by exciting half of the atoms into a spin-up state and half into a spin-down one. With the interface is place, they reversed the magnetic field gradient, inducing a force on the atoms equivalent to the buoyant force seen in conventional Rayleigh-Taylor instabilities. As shown above, the interface first warped, then developed Rayleigh-Taylor mushrooms and eventually became turbulent. (Image and research credit: Y. Geng et al.; via Physics World)
In “Re:Birth,” videographer Vadim Sherbakov explores the fascinating patterns of ferrofluids, which suspend tiny ferrous particles in another liquid, often oil. When this magnetic liquid is mixed with ink or paint, its black lines take on a labyrinthine appearance. The result is rather psychedelic, especially with Sherbakov’s bold colors. (Video and image credit: V. Sherbakov)
As part of the demolition of a decommissioned coal-fired power plant in Nottinghamshire, workers simultaneously demolished eight cooling towers. The video is here. As the towers collapse, smoke and dust gets blown both out of the base and up each tower. The flow details are fascinating. The plumes have rings in them, perhaps related to how the blast’s waves reflect in the tower or how the structure itself fails. Vortex rings curl up as the rising plumes mix with the surrounding air. If you’re anything like me, you’ll have to replay it several times! (Image credit: BBC; submitted by jshoer)
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)
