Celebrating the physics of all that flows with Nicole Sharp, Ph.D.
- Profile
“Opening the Vortex”
Photographer Lisa K. Kuhn captured a spectacular lenticular cloud over Mount Shasta in this image from the Sony World Photography Awards. These lens-shaped clouds occur most often near mountains and other terrain that forces air to flow up and over it. As the air cools, water condenses out, forming the cloud. When the air flows…
Understanding Pollen Dispersal
When the wind blows, trees shift and sway, reconfiguring their shape and their leaves in response. For parts of the year, that flow can also pluck pollen grains off the tree, carrying them on the winds. A new computational simulation models this pollen dispersal from a tree, with the aim of eventually integrating into a…
Setting the Stripes on a Tiger (Cake)
A tiger skin cake forms a distinctive pattern of light and dark patches as it bakes. Its current popularity seems to have expanded outward from China; I found a lot of Swiss-roll-style recipes that use it as an outer wrapper. Here, researchers look at how the wrinkled surface forms. The viscous batter quickly forms a…
Waves on Other Planets
On Earth, most waves form when wind blows across the water. The shear and added energy from the wind ripples the surface, eventually building up waves (through the Kelvin-Helmholtz instability). The same process should happen anywhere else where wind and open liquid surfaces meet–even on other planets. To explore this, researchers built a new model,…
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,…