Today, enjoy this moody black-and-white short film of storm timelapses. Photographer Mike Olbinski is a master of this subject. I never tire of watching his towering convective supercell thunderstorms or his picturesque microbursts. The lightning-lit clouds in the latter half of the film are particularly spectacular (assuming you do not have sensitivities to flashing lights). And there are a few haboobs and a tornado in there for good measure, too. (Image and video credit: M. Olbinski)
With the right balance of viscosity and surface tension, many fluid combinations can form fractal or dendritic patterns. Here, researchers use a drop of food coloring atop a mixture of water and xanthan gum. Depending on the concentration of gum (and the age of the viscous fluid) different fractal patterns spread quickly across the surface. (Image and video credit: R. Camassa et al.)
Inspired by honeybees and their ability to surf on capillary waves of their own making, researchers have developed SurferBot, a low-cost, untethered, vibration-driven surf robot. Built on a simple 3D-printed platform, the bot has a vibration motor powered by a simple coin cell battery. As the motor vibrates, it propels the bot forward (Image 2). With the motor placed off-center, the bot’s vibrations create larger capillary waves at the rear of the bot than at the front (Image 3). It’s this asymmetry that drives the robot forward. The flow pattern created by the bot’s propulsion is impressively strong (Image 4) and consists of a pair of counter-rotating vortices trapped ahead of the bot and a strong central jet in its wake.
Best of all: SurferBot is a great platform for educational experimentation, costing <$1 apiece! (Image and submission credit: D. Harris; research credit: E. Rhee et al.)
To our eyes, a soap bubble appears to pop instantly, but when observed in high-speed video, the process is far more complex. In this video, the Slow Mo Guys pop human-sized bubbles, giving us an opportunity to appreciate the rupture process at speeds up to 50,000 frames per second.
Once the rupture starts, the hole spreads very symmetrically. But as the hole grows, the remaining soap film starts distorting. As Gav and Dan observe, the far side of the bubble actually wrinkles up before the rupture front arrives and tears the remaining fluid into droplets! (Image and video credit: The Slow Mo Guys)
Immiscible liquids — like oil and water — do not combine easily. Typically, with enough effort, you can create an emulsion — a mixture formed from droplets of one liquid suspended in the other — like the one above. But a team of researchers have taken mixing immiscible liquids to a new level using their Vortex Fluid Device (VFD).
Longtime readers may remember the group from their Ig-Nobel-winning demonstration of unboiling an egg, but this time the team is used the VFD to mix and de-mix immiscible liquids. As shown in the video below, the VFD is essentially a fast-spinning tube tilted at a 45-degree angle. As it spins, the liquids inside are forced into thin films with very high shear rates — high enough that immiscible liquids like water and toluene are forced together without forming an emulsion. Essentially, the mechanical forces mixing the liquids are strong enough to overcome the chemistry that typically keeps them apart.
Impressively, the device manages this without using harsh surfactants or catalysts that other methods rely on. As a result, the technique offers a greener method for mixing chemicals for pharmaceuticals, cosmetics, food processing, and more. (Image credit: pisauikan; research credit: M. Jellicoe et al.; video credit: Flinders University; submitted by Marc A.)
Icy crystals burst forth against a dark background in Thomas Blanchard’s short film “Belletrix.” The process is one of chemical crystallization. Blanchard supersaturates a chemical in a dish of hot water, then cools the fluid, which then spontaneously crystallizes when disturbed. Depending on the solution’s temperature, the crystals vary from feather-like to radial stars, each reflecting, expanding, and overlapping to cover the full surface. (Image and video credit: T. Blanchard)
With the low sun angle of dawn, the details of this cloudscape stand out. Captured by an external camera on the International Space Station, this image shows cloud formations over the northwest Atlantic. In the foreground, towering cumuli mark rising plumes of warm, moist air evaporating from the ocean. Beyond those clouds, a flat anvil cloud spreads horizontally after a temperature inversion prevented it from rising any further. (Image credit: NASA; via NASA Earth Observatory)
Compared to its interior, the surface of our sun is a cool 6,000 degrees Celsius. But beyond the surface, the sun’s corona heats up dramatically through interactions between plasma and strong magnetic fields. The exact mechanisms of this interaction have been mostly theoretical thus far, but a recent laboratory experiment has validated a part of that theory.
One explanation for coronal heating posits that the strong magnetic fields can accelerate magnetohydrodynamic waves called Alfvén waves to speeds faster than sound, and that at this crossover point, changes occur in the waves’ behavior. Using liquid rubidium, researchers were able to observe this crossover under laboratory conditions, confirming that the Alfvén waves change at the speed of sound in exactly the manner predicted by theory. (Image credit: NASA SDO; research credit: F. Stefani et al.; via Physics World)
Most cooks know that their frying oil isn’t hot enough if dropping the food in doesn’t create a furious burst of bubbles. But the canniest cooks know they can check the temperature just by listening to the sound made when inserting a utensil, like a wooden chopstick. When oil nears the right temperature, a cloud of bubbles forms around the utensil, leading to a flurry of sound as those bubbles break.
In this video, researchers explore the sound and bubble dynamics together as a function of temperature. They show how the final sound carries the signature of the its bursting bubble, too. So next time you’re getting ready to fry and you can’t find your thermometer, don’t panic. Just listen! (Image and video credit: A. Kiyama et al.)
Years ago, physicists discovered that water flows with surprisingly little friction through narrow carbon nanotubes. At our scale, flow behavior is typically the opposite: there’s greater friction (and, thus, slower flow) in a narrower pipe. To unravel the mystery, researchers had to delve into quantum mechanics and model the interactions between the atoms of a water molecule and the electrons of the carbon atom. Essentially, this meant building a quantum picture of the liquid-solid interface inside the nanotube.
The team found that the electrons of the nanotube exert a drag-like force on the water molecules, creating friction that slows the flow. Since narrow nanotubes have fewer electrons than larger tubes, there is less friction on the flow and the water flows faster! (Image credit: cintersimone; research credit: N. Kavokine et al.; via SciAm; submitted by Kam-Yung Soh)