Celebrating the physics of all that flows with Nicole Sharp, Ph.D.
- Profile
Slapping Sheets
Here fluid is ejected as two flat plates collide, creating a sheet of silicone oil. The initially smooth sheet forms a thicker ligament about the edge. Gravity causes the sheet to bend downward like a curtain, and growing instabilities along the ligament cause the development of a wavy edge. The points of the waves develop…
The Evolution of Icicles
The time-lapse video above shows the growth of icicles of various compositions under laboratory conditions. Many icicles in nature exhibit a rippling effect in their shape, which some theories attribute to an effect of lower surface tension in some liquids. Here researchers show the icicle growth of three liquids: pure distilled water, and water with…
Hot Items Sink Faster
This combined video shows the fall of a heated centimeter-sized steel sphere through water. From left to right, the sphere is at 25 degrees C (left), 110 degrees C (middle), and 180 degrees C, demonstrating how the Leidenfrost effect–which vaporizes the water in immediate contact with the sphere–can substantially reduce the drag on a submerged…
A Colorful Rinse
In this image a jet of water (clear/white) is rinsing a solution of polyacrylamide (PAM; blue) off a silicon surface. In the center, a hydraulic jump marks the interface where fast-moving laminar flow changes to a slower turbulent one. At the same time, the water, which is less viscous than the PAM, creates viscous finger-like…
Inksplosion
Artist Pery Burge utilizes surface tension driven flows created with inks and water for much of her work. As mesmerizing as this is in still-life, it is more lovely still to see it develop and evolve in motion. The explosive outward motion of the ink is driven by the addition of a liquid with a…
Shedding Vortices
The von Karman vortex street of shed vortices that form the wake of a stationary cylinder are a classic image of fluid dynamics. Here we see a very different wake structure, also made up of vortices shed from a cylindrical body. This wake is formed by two identical cylinders, each rotating at the same rotational…
Mixing Physics
One of the most commonly observed fluid instabilities is the Rayleigh-Taylor instability, which occurs between fluids of differing densities. It’s most often seen when a denser fluid sits over a lower density fluid. In the video above, this is demonstrated experimentally: a lower density green fluid mixes in with the clear, higher density fluid. This…
Sloshing in a Bouncing Sphere
The sloshing of liquids inside solids is usually presented as a difficulty to overcome, as with the transport of tanks, the motion of fuel in satellites, or even the problem of walking with a full cup of coffee. But liquids also make a very effective damper, as in the case of a bouncing ball partially…
Antarctic Ice Flows
Even frozen ice moves and flows, though too slowly to see with the naked eye. By combining satellite imagery from NASA, JAXA, CSA, and ESA, researchers were able to map the flow of ice across Antarctica, discovering ice streams (shown in blue and purple above) that can move hundreds of meters a year. The dynamics…
Countertop Fliers
http://s3.amazonaws.com/scifri-videos/flyer-121611.mp4 In this video, researcher Leif Ristroph and his colleagues have used a clever way to simulate flapping flight, not by actuating their fliers but by oscillating the flow. The flow is driven by a speaker, which causes the air above it to move up and down. Using straws to simulate the honeycomb flow conditioners…