Celebrating the physics of all that flows with Nicole Sharp, Ph.D.
- Profile
Lensing in a Straw
While doing the sort of experiment only a kid or a scientist would pursue – namely, staring down a straw – Dianna noticed that water in a straw creates a lens-like magnification effect as the straw moves or down. This happens thanks to the curvature of the air-water-straw interface. Because water has strong surface tension, it…
Volcanic Plume
Astronauts aboard the International Space Station captured this dramatic image of Raikoke Volcano’s eruption in late June. This uninhabited Pacific Island is part of the Kuril Islands off mainland Russia. The hot plume of ash and volcanic gas rose until its density matched that of the surrounding air, at which point it could only expand horizontally.…
The Skipping Dambusters
During World War II, the Allies developed “dambuster” bombs that skipped repeatedly off the surface of the water before striking their target. The goal was to cleverly bypass their enemies’ defenses both above and below the surface. Although the original dambusters used spinning spheres, the ricochet physics works for many other configurations as well; essentially, the physics…
Testing Vesicles
In biology, vesicles contain a liquid surrounded by a lipid membrane. The characteristics of that membrane – like its stiffness – can change over time in ways that indicate other changes. For example, vesicles carrying HIV become stiffer as they grow more infectious. In the past, to observe these properties scientists used atomic force microscopes, which require…
Pouring a Liquid Mirror
In this video, the Slow Mo Guys play with liquid gallium, giving us a chance to see how molten metals behave (outside of, say, the Terminator movies). Near its melting point, gallium is about six times denser than water, with a viscosity three times higher, and a surface tension about ten times greater. So how do those…
Liquid Magnets
Ferrofluids – those distinctively spiky liquids – are made up of magnetically sensitive nanoparticles in a carrier liquid, and although they respond to applied magnetic fields, they retain no magnetism outside of that field. But researchers have now succeeded in making actual liquid magnets. Shown above, these drops also contain ferromagnetic nanoparticles. But unlike traditional ferrofluids,…
Entraining Bubbles
If you stand on a bridge and watch the current flow past pylons below, you’ll see disturbances marking the wakes. Dragging a rod – or an oar – at a high enough speed through the water creates something similar: a wavy cavity in the fluid surface that surfs along behind the rod. The faster you pull the rod,…
The Snowy Salt of the Dead Sea
At nearly 10 times saltier than the ocean, the Dead Sea is one of the saltiest places on Earth, and since 1979, scientists have observed it growing even saltier as snow-like salt precipitates to the bottom of the lake. Numerical simulations have now confirmed that this salt-fall is the result of double-diffusive salt fingers. Here’s how the mechanism works:…
Superwalkers
Walking droplets – drops that bounce their way across a pool of the same liquid without coalescing – have fascinated researchers in recent years with their unusual behaviors, some of which mimic quantum phenomena. In a new experiment, researchers vibrate the pool at two frequencies simultaneously, which helps support much larger droplets, known as superwalkers. When the two…
Dissolving Pills
This short film from Macro Room shows how pills dissolve in timelapse. Dissolution is a complex process driven both by flow and chemical concentration. Any small motion in the water helps erode the surface, and as the chemicals dissolve, the subsequent variations in the concentration drive additional flow. This is why we often see a turning point in…