Celebrating the physics of all that flows with Nicole Sharp, Ph.D.
- Profile
Holding Pipes in Place
Newton’s 3rd law states that any action has an equal and opposite reaction. Often engineers use this to our advantage; the thrust from expelling propellants is what lifts our rockets to space. But sometimes those reactions are undesirable, as illustrated in this Practical Engineering video with underground pipes. Anytime flow through the pipe is forced…
Singing in the MRI
We rarely consider just how complex the process is when we speak or sing. Sound waves produced in our larynx are shifted and amplified by the geometry of our throats, mouths, sinus cavities, tongues, and lips. This video provides a glimpse of that hidden complexity through a trained vocalist singing inside an MRI machine. He…
Sliding Foams
What happens when a foam interacts with a sliding surface? That’s the question at the heart of this study, which finds three major regimes of foam-surface interaction. On smooth surfaces (Image 1), foams will simply slide against the wall without sticking or deforming. When surface roughness is about as large as the foam’s wall thickness…
Bristling Sharkskin Fights Separation
The speedy shortfin mako shark has a secret weapon to fight drag: bristling denticles that line its fins and tail. Denticles are tiny, anvil-shaped enamel scales on the mako’s skin. In the photo above, each one is about 100 microns across. Under normal conditions, with flow moving over the shark from nose to tail, the…
Expanding Water Beads
In this timelapse, we see hydrogel beads expanding as they absorb water. There are some interesting subtleties to the physics here. Notice how, in the Petri dish segments, the beads shift from a single crystalline structure to several smaller structures. I suspect those shifts are driven by the dropping water level, which changes how surface…
Icy Swirls
Rafts of sea ice follow swirling eddies in this satellite image of the Gulf of St. Lawrence. Just as with phytoplankton blooms and sediment, this thin sea ice can be moved by wind and currents to reveal hidden flow patterns. Experimentalists use many similar diagnostics that introduce bubbles, particles, smoke, and other tracers into flows…
Steering as a Boxfish
Coral reefs are full of odd-looking denizens, but one of the funniest-looking ones must be the boxfish. This family of fish lives up to its name; their bodies feature an angular, bony carapace that helps protect them. But you don’t have to be a fluid dynamicist to wonder how in the world they swim with…
Mixing Leidenfrost Drops
When placed on a very hot, patterned surface, droplets will self-propel on a layer of their own vapor. Here, researchers use this to drive droplets to coalesce so that they can observe how well they mix. After their head-on collision, the merged droplets have two major forces fighting in them: surface tension, which tries to…
Choosing Swimming Over Flight
When studying modern birds it quickly becomes apparent that they can either be good at swimming or at flying, but not at both. The characteristics that make wings good for flying are diametrically opposed to those that make for a good swimmer. So most species have chosen to invest in one strategy or the other.…
Breaking Up Granular Rafts
Particles at a fluid interface will often gather into a collection known as a granular raft. The geometry of the interface where it meets individual particles, combined with the surface tension, creates the capillary forces that attract these particles to one another. Colloquially, this is called the Cheerio’s effect; it’s the same physics that draws…