Celebrating the physics of all that flows with Nicole Sharp, Ph.D.
- Profile
Supersonic Jet Interaction
When supersonic jets get emitted into rarefied air, they behave differently than they do in regular atmospheric conditions. Here, researchers picture three different configurations these jets can take. In the top image, the jets are close enough together that they appear to merge into a narrow supersonic jet. In the middle image, the jets are…
The Dragon’s Eye
Looking down on a Icelandic geothermal pool gives a view into a dragon’s eye in this drone image by photographer Miki Spitzer. It won the Gold distinction in the World Nature Photography Awards’ “Planet Earth’s landscapes and environments” category. I particularly like how the mineral-rich stains left by evaporating water highlight the texture of the…
Seeing Stress in an Avalanche
Researchers sometimes study avalanches and other granular flows in a rolling drum, where grains can cascade down continuously. Here, the twist is that they’ve done it with photoelastic disks, which show stress patterns when viewed under crossed polarizing filters. In any given moment, the contacts between neighboring particles form a force chain that lights up…
How the “Impossible Torpedo” Worked
The Brennan torpedo — a 19th-century version of the weapon — was launched by pulling a cable out the back. As counterintuitive as it sounds, pulling this cable backward propelled the torpedo forward. To show how this is possible (while side-stepping the messy specifics of how the turning propeller thrusts the vehicle forward), Steve Mould…
Jets From Impact
When a test tube of liquid hits a surface, the curvature of the meniscus focuses the rebounding fluid into a jet. In this video, researchers show some of the many variations they’ve explored on these experiments–from changing the depth of the fluid and the shape of the container, to changing the working fluid to honey…
Liquid Pulleys and Gears
In mechanical systems, gears and pulleys transmit rotation from one location to another. Here, researchers explore a fluid dynamical version of such systems. The set-up consists of two rotors contained in a cylindrical corral filled with a water-glycerin mixture. One of the rotors is active, marked here with orange; the other (blue) one is passive,…
“Spiralling Textures”
Wet fur forms a spiral of spiky hairs in this image by photographer Ben Dalgleish. For thin and flexible fibers like hair, a little moisture lets them clump together, forming stiffer (but still flexible) shapes. The technical term for this water-meets-flexible-solid phenomenon is elastocapillarity, and it lets you do things like wind a wire with…
Inside an Ear
Our ears, like those of many other animals, convert mechanical signals to electrical ones, through a Rube-Goldberg-esque series of transformations. External sound waves make their way down the soft tube of the ear canal, which funnels them to a thin-walled cone, the eardrum, that’s about half as large as a dime. Here, the vibrating air…
Plucking Droplets
A sudden breeze can pluck droplets hanging from a stem. Here, researchers recreate that phenomenon in the laboratory. With a close-up view and high-speed images, we can enjoy every detail of the detachment and break-up. As the wire pulls away, it drags a liquid sheet off the droplet. The thicker rims on either side of…
Fluids Can Fracture
Fracture is a sudden, brittle breaking-apart that we generally associate with solid materials that get stressed too far. Some viscoelastic, non-Newtonian fluids have been known to fracture, but that was generally thought to be unusual. But a recent study turns that idea on its head, revealing that even simple, albeit highly viscous, liquids can fracture.…