Celebrating the physics of all that flows with Nicole Sharp, Ph.D.
- Profile
Drying Unaffected by Humidity
Water evaporates faster in dry conditions than in humid ones, but the same isn’t true of paint. Instead, paint’s drying time is largely independent of the day’s humidity. That’s because of paint’s long chains of polymers. As water in the paint evaporates, these polymers are drawn to the surface, forming a viscoelastic layer that hinders…
“Coat or Collapse?”
Imagine a layer of particles sitting at the interface between oil and water. Known as a granular raft, these particles can interact in interesting ways with other objects. Here, researchers experiment with allowing different shapes to fall through the raft. At slow speeds, the raft deforms to coat the object, even if it has a…
“Alive”
In “Alive,” filmmaker Christopher Dormoy explores acrylic paints and the variety of ways in which the medium can be used. From a fluids perspective, there’s dripping, viscous flow, turbulent eddies, billowing plumes, and “accidental painting” due to density-driven instabilities. It’s a fun tour of fluid phenomena in art. What examples do you spot? (Video and…
Thermal Slipping
A particle suspended in a liquid typically jitters haphazardly about as it’s struck randomly by nearby liquid molecules. But when a temperature gradient is applied to the liquid, that random motion instead becomes directional. In a recent study, researchers directly mapped the motions underlying this thermophoresis. In their experiment, the team placed a 7-micron sphere…
Beneath the Surface
Signs of a ship’s passage can persist long after it’s gone. The churn of its propellers and the oil leaked from its engines leave a mark on the water’s surface that, in some cases, is visible even from orbit. But the frothy wake of a ship is no easy place to measure; there are simply…
Frictional Fingers
Air pushes into a thin gap filled with water and granular particles in the labyrinth-like image above. The encroaching air pushes grains like a bulldozer’s blade, building up a compacted wall. The invasion continues until the pressure of the air is countered by the combined capillary and frictional forces of the wet grains. Researchers built…
Inside a Soap Bubble
Every child learns to blow soap bubbles, but it’s rare that we have a chance to look inside them and see the flow there. In this poster, researchers seed a growing bubble with olive oil droplets, then illuminate them with a laser. This provides a glimpse inside the bubble. In the center, we see the…
Icelandic Glow
Solar wind particles slam into the atmosphere near Earth’s poles, creating billowing curtains of glowing plasma known as auroras. Beneath the earth, molten rock seethes and flows, squeezed up fissures to release explosive gases and spurts of lava to the surface world. These natural phenomena are captured in the left and center of this image,…
Sliding on Fibers
Water drops slide down spiderwebs, along the spines of desert plants, and across the armored exterior of horned lizards. Thin, grooved surfaces like these pop up frequently in nature when organisms need to direct water. A recent study of droplets sliding on fibers suggests why. A drop sliding down a fiber is constantly shrinking, leaving…
Shaking on Impact
When objects impact water with enough speed, they create a smooth-walled, air-filled cavity around and behind them. Here, the impacting object is one with some give, like a spring. The initial impact squishes the object, setting it to oscillating along its length. The result is a wavy cavity. The stiffer the object, the more frequent…