Celebrating the physics of all that flows with Nicole Sharp, Ph.D.
- Profile
Fizzy Droplets
Leidenfrost drops surf on a layer of their own vapor, created by the high temperature of a nearby surface relative to their boiling point. These Leidenfrost drops can self-propel and skitter and skate across a surface, but they’re not the only droplets that do this. In this video, researchers show how a drop of carbonated…
Jumping Droplets
From butterfly wings to lotus leaves, many surfaces in nature are shaped to repel water. This typically means roughness on the scale of tens of nanometers, which helps trap air between water and the surface. Droplets can still form on these surfaces, but when they merge, the sudden excess of surface energy sends the coalesced…
Prehistoric Seiche
Sixty-six million years ago, a meteorite impact in modern-day Mexico wiped out the dinosaurs and most other living species of the time. To call the event catastrophic feels like an understatement. At the site of impact, rocks and animals were vaporized. Further away, molten rock condensed into glass beads that form a geological layer found…
The Beauty of Flames
The flickering yellow and orange flames most of us are used to thinking of are rather different from the flames researchers study. In this video, the Beauty of Science team offers a short primer on different flame shapes studied in combustion, including laminar, swirling, and jet flames. Each has its own distinctive character and may…
Vibrating in the Flow
Objects can obviously affect flows, but that’s not a one-way street. Flows can also affect objects, even ones as simple a circular cylinder. If you live somewhere with traffic lights mounted to a horizontal bar, you’ve probably seen this. On a windy day, the beam holding the traffic lights will oscillate up and down. This…
Communication Between Microswimmers
The elongated cells of Spirostomum ambiguum swim using hair-like cilia, but when threatened, the cells contract violently, sending out long-range hydrodynamic waves, like those visualized above. Along with these waves, the cells release toxins aimed at whatever predator threatens them. In a colony, these waves act like a communication beacon. The swirl of a previous cell’s…
Soap Film Evolution
The beautiful colors of a soap film reflect its variations in thickness. As a film drains and evaporates, it turns to shades of gray and black as it gets thinner. More than fifty years ago, one scientist proposed a free-energy-based explanation for how such ultrathin films might evolve. But it’s taken another half a century…
Paddling
When I lived in New England, I often spent summers paddling around a lake in either a kayak or canoe. Every stroke was an opportunity to stare down into the dark water and watch how the flow curled around my oar. Here you see a bit of what that looks like from underwater. The animation…
Foam Collapse
Introduce the right additive and the bubble arrays in foam will collapse catastrophically. What you see above is high-speed video of a quasi-two-dimensional soap bubble foam collapsing. There are two main mechanisms in the collapse. The first is a propagating mode. When one section of the film breaks, a stream of liquid from the broken…
The Shaky Life of a Droplet
An evaporating drop of ouzo goes through several stages due to the interactions of oil, alcohol and water. If you turn the situation around by placing a drop of (blue-dyed) water in a mixture of alcohol and anise oil (top image), you get some similarly odd behavior. The drop of water shimmies and grows as…