Celebrating the physics of all that flows with Nicole Sharp, Ph.D.
- Profile
Green Fingers
Differences in surface tension between two layers of fluid can cause fascinating finger-like instabilities. Here glycerol is spread in a thin film on a silicon wafer. Then a wire coated in oleic acid, which has a lower surface tension than glycerol, was touched to the wafer. As the oleic acid spreads across the film surface,…
“Millefiori”
In “Millefiori” artist Fabian Oefner mixes watercolors with ferrofluids to create bright fluid microcosms. Each photograph represents an area about the size of a thumbnail. Ferrofluids contain iron-based nanoparticles suspended in a carrier fluid and thus respond to magnetic fields. They can form sharp points, labyrinthine mazes, or even brain-like patterns depending on the magnetic field and…
Dribbling Droplets
Ethanol droplets on a hot copper plate bounce under the influence of electrostatic forces from a charged rod. The temperature of the plate is high enough that the droplet is supported by a thin vapor film, which is what keeps it from wetting the plate. Ethanol does not have the strong polarity that water does,…
Polygonal Jumps
Hydraulic jumps occur when a fast-moving fluid enters a region of slow-moving fluid and transfers its kinetic energy into potential energy by increasing its elevation. For a steady falling jet, this usually causes the formation of a circular hydraulic jump–that distinctive ring you see in the bottom of your kitchen sink. But circles aren’t the…
Spray Starch
High speed video of of spray starch from a can. Once the initial transients die down, a cone-shaped annular sheet forms. Disturbances propagate in the sheet, tearing it into filaments that break down into droplets. Beautiful complexity hidden in a simple everyday device. (Video credit: John Savage)
Dynamic Leidenfrost Impact
The Leidenfrost effect occurs when a liquid encounters a solid object much hotter than the liquid’s boiling point, like when water skitters on a hot griddle or someone plunges a hand in liquid nitrogen. A thin layer of vapor forms between the liquid and the solid, thereby (briefly) insulating the remaining liquid. The Leidenfrost effect…
The Archer Fish’s Arrows
The archer fish hunts by shooting a jet of water at insects in the leaves above and knocking them into the water. How the fish achieve this feat has been a matter of contention. A study of high-speed video of the archer’s shot shows that fluid dynamics are key. The fish releases a pulsed liquid…
Rebounding
A ping pong ball bounces off a puddle, drawing a liquid column upward behind it. This photo shows the instant after the fluid has disconnected from the ball, allowing it to rebound without further loss of momentum to the fluid. The fluid column begins to fall under gravity, the tiny undulations in its radius growing…
Following a Breaking Wave
It’s fascinating to sit on the beach and watch the waves roll in and break, but rarely do we get a view like the one in this video. Here researchers have created a breaking wave in a wave tank and recorded the wave as it travels the length of the tank with a high-speed camera…
Peering Inside the Kettle
Here natural convection is explored experimentally in a quasi-2D environment. The researchers demonstrate how this phenomenon, which is much like that seen in a boiling pot, can be investigated by measuring the refractive distortions caused by the thin heated fluid layer. They also demonstrate types of boiling that can occur. Typically, bubbles nucleate at the heated…