Celebrating the physics of all that flows with Nicole Sharp, Ph.D.
- Profile
Sunglinting Seas
Sunlight reflecting off the Earth can reveal a remarkably rich picture of our planet’s activity. The silver-gray areas seen in this satellite image are sunglint, where lots of light is reflected back to space. Sunglint occurs in regions with very few waves; more waves – like in the bluer areas – mean more directions in…
Surfing Mists
Watch your hot cup of coffee or tea carefully, and you may notice a white mist of tiny micron-sized droplets hovering near the surface. These microdroplets are a little understood part of evaporation. They form over a heated liquid, levitating on vapor that diffuses out from them and reflects off the liquid surface. (This is…
Pelican Diving
Pelicans, like many sea birds, are aerial divers. They spot their prey from high above, bank, and dive into the water to catch the fish. Although they hit the water at high speeds, pelican diving techniques differ somewhat from plunge divers like gannets or boobies. Pelicans are only aiming for a shallow dive, so they…
Controlling Leidenfrost Drops
On a surface much hotter than their boiling point, droplets can surf on a layer of their own vapor due to the Leidenfrost effect. Recent research has shown that textured surfaces like ratchets can create corrals, traps, and mazes for such droplets. Here, researchers manipulate the propulsion of Leidenfrost drops using non-parallel grooves instead. When…
Convection
Blue paint in alcohol forms an array of polygonal convection cells. We’re accustomed to associating convection with temperature differences; patterns like the one above are seen in hot cooking oil, cocoa, and even on Pluto. In all of those cases, temperature differences are a defining feature, but they are not the fundamental driver of the…
Dam Failure
In a recent video, Practical Engineering tackles an important and often-overlooked challenge in civil engineering: dam failure. At its simplest, a levee or dam is a wall built to hold back water, and the higher that water is, the greater the pressure at its base. That pressure can drive water to seep between the grains…
Self-Healing Bubbles
Soap films have the remarkable property of self-healing. A water drop, like the one shown above, can pass through a bubble (repeatedly!) without popping it. This happens thanks to surfactants and the Marangoni effect. Surfactants are molecules that lower the surface tension of a liquid and congregate along the outermost layer of a soap film.…
Creating Clouds
Despite their ubiquity and importance, we know surprisingly little about how clouds form. The broad strokes of the process are known, but the details remain somewhat fuzzy. One challenge is understanding how nucleation – the formation of droplets that become clouds or rain – works. A recent laboratory experiment in an analog cloud chamber suggests…
Flames in Freefall
Gravity is such an omnipresent force in our lives that we frequently forget how strongly it affects our daily experiences and how differently nature behaves without it. A wonderful example of this is the simple flame of a candle. On Earth, a candle flame is tear-drop-shaped and elongated, burning hotter near the bottom and glowing…
Island Wakes
One of my favorite aspects of fluid dynamics is watching how patterns repeat at all kinds of scales. The cotton-candy-colored image above is a false-color satellite image of the island Tristan da Cunha (left), a volcanic island group in the South Atlantic. The prevailing winds, oriented roughly left to right in the image, flow over…