Celebrating the physics of all that flows with Nicole Sharp, Ph.D.
- Profile
Sunset Swirls
This gorgeous photograph of Kelvin-Helmholtz clouds was taken in late December in Slovenia by Gregor Riačevič. The wave-like shape of the Kelvin-Helmholtz instability comes from shear between two fluid layers moving at different relative speeds. Here on Earth, clouds like these are often short-lived, but we see similar structures in the atmospheres of gas giants…
Adjusting for Gusts
In flight, birds must adjust quickly to wind gusts or risk crashing. Research shows that the structure of birds’ wings enables them to respond faster than their brains can. The wings essentially act like a suspension system, with the shoulder joint allowing them to lift rapidly in response to vertical gusts. This motion keeps the…
High Tide
Broad Sound, in eastern Australia, is home to some of the most extreme tidal swings in the world, with more than ten meters difference between high and low tides. The bay’s peculiar geography, along with the topography of nearby reefs, combine to cause the large tides. This color-enhanced satellite image shows the bay at high…
Lake Stars
As snow-covered frozen lakes melt, stars appear on their surface. These lake stars form around holes in the ice where (relatively) warm water seeps up into the slush layer. The stars form through a competition between thermal effects and flow through the porous snow. Researchers have built mathematical models that capture the first-order effects, like…
Slow Mo Pulse Jet Engine
Pulse jet engines rely on their shape to maintain combustion without moving parts. The pressure waves that travel through the engine pump fresh oxygen into the combustion chamber and then ignite it with exhaust remaining from the last cycle. In this Slow Mo Guys video, we get to see that process in action. It’s a…
“Mist and Water”
Years ago, I drove through the Blue Ridge Mountains on a wet and misty New Year’s Day. The fog that clung to the dark trees made the whole world quiet and surreal. And although Mike Olbinski’s “Mist and Water” takes place on the opposite side of the country in Oregon, that’s what the video reminds…
Dual Structure of Water
Water is so ubiquitous in our lives that we rarely recognize just how strange it is. For example, when pure liquid water is supercooled well below its freezing temperature, it takes on not one but two molecular arrangements, one of which is high-density and one of which is low-density. Theory had posited this configuration for…
Eyes on the Sun
Though it may look like the Eye of Sauron, this image is actually one of our best-ever glimpses of a sunspot. Captured by the Daniel K. Inouye Solar Telescope, this sunspot is larger than our entire planet, yet we can see details as small as 20km across. The dark central region of the image is…
Seismic Events Reveal Ocean Temperatures
Decades ago, researchers proposed sending sound waves through the ocean to measure its temperature. Although the technique worked, it ran into noise pollution issues, but now it’s back, using naturally-occurring seismic events as the sound source. When fault lines shift, they generate seismic waves that travel through the ocean as sound. When they reach a…
The Strangeness of Sand
Sand and other granular materials can flow, jam, and transmit forces in counterintuitive ways. This Lutetium Project video gives a nice overview of some of these bizarre properties. Many of sand’s odd characteristics come from the way forces move through grains that touch. Around 5:20 there’s a demo of one of these effects: the Janssen…