Celebrating the physics of all that flows with Nicole Sharp, Ph.D.
- Profile
Shock Waves Drive Nova Brightening
New observations of nova V906 Carinae have provided some of the first direct evidence that the observed brightening of these stellar objects is driven by shock waves. Novae form when hydrogen from a companion star settles onto a white dwarf. Once enough material accumulates, the white dwarf blows out the excess hydrogen in a donut-shaped…
Cavitation Through Acceleration
Cavitation refers to the formation of destructive bubbles of vapor within a liquid. Traditionally, we think of it as occurring when the velocity in a flow becomes high enough for the pressure to drop below the local vapor pressure, causing bubbles to form. This is what we see around turbine blades and ship propellers. But…
‘Aila’Au: Forest Eater
The 2018 eruption of Kilauea was a dramatic example of nature’s power. This short film shows both some familiar views of that eruption as well as new ones. I found the slow-moving wall of cooling a’a lava eating the forest particularly intriguing, not least thanks to the glass-like sound of the lava advancing. Whether slow-moving…
Crisscrossing Wave Clouds
Crisscrossing lines of wave clouds mark the wake of the Sandwich Islands in this satellite image. The tallest islands in the chain thrust rocky peaks more than 1000 meters above sea level, disrupting winds flowing across the ocean. Incoming air is forced up and over the mountain, which puts it at odds with the surrounding…
COVID-19 and Outdoor Exercise
By now you’ve probably come across some blog posts and news articles about a new pre-print study looking at the aerodynamics of running and the potential exposure to exhaled droplets. And you may also have seen articles questioning the accuracy and validity of such simulations. I’ve had several readers submit questions about this, so I…
Watching a Droplet Freeze
Whether it’s rain hitting an airplane wing or droplet-based 3D printing, the dynamics of a droplet impacting and solidifying on a surface are important. This new study observes the process from below, tracking the progress of freezing on a scale of hundreds of nanoseconds. All three of the drops you see above are liquid hexadecane.…
Tektites and Spinning Fluids
Tektites, like obsidian, are a naturally-occurring glass formed from molten rock. But tektites are often dumbbell or figure-8-shaped because they form in midair from spinning bits of fluid sent skyward after the crash of a meteor. In this video, Steve Mould takes us through the process and discusses some recent work by scientists who’ve created…
“Focus, Vol. 1”
In “Focus, Vol. 1,” photographer Roman De Giuli follows colorful droplets as they roll along, chase one another, and burst. You may notice that many of the drops seem attracted to one another. This is actually a surface tension effect caused by the dimples the droplets create on the surface; it’s the same effect responsible…
Why Animals Shake Themselves Dry
For many animals, letting themselves air-dry is not an option. They would become hypothermic before their wet fur dried completely. This is why dogs and many other furry mammals shake themselves dry. It’s a remarkably efficient process, too, removing the majority of water from fur in a matter of seconds. The key is to shake…
Bouncing Off Hydrophilic Surfaces
Droplets typically bounce off hydrophobic surfaces due to air trapped beneath the liquid that prevents contact between the drop and surface. But even extremely smooth, hydrophilic surfaces can elicit a bounce under the right circumstances, as shown in a new study. The key is that the droplet must bounce at exactly the right speed. If…