Celebrating the physics of all that flows with Nicole Sharp, Ph.D.
- Profile
Dandelion Flight, Continued
Not long ago, we learned for the first time that dandelion seeds fly thanks to a stable separated vortex ring that sits behind their bristly pappus. Building on that work, researchers have now published a mathematical analysis of flow around a simplified dandelion pappus. Despite their simplifications, the model captures the flow observed in the previous experiments…
Prehistoric Filter Feeders
Earth’s earlier ages are filled with enduring mysteries about the plants and creatures that lived and died long before humanity. Many of these organisms, like the aquatic Ernietta shown above, are known only from scattered fossil remains. Yet fluid dynamics is helping us understand how Ernietta lived and fed some 545 million years ago. Ernietta were sack-like organisms consisting of stitched-together…
Titan’s Dragonfly
Last week, NASA announced its next New Frontiers mission: a nuclear-powered drone named Dragonfly heading to Titan. This astrobiology mission is set to search our solar system’s second largest moon for signs of life. It’s exciting aerodynamically, as well, since Titan’s thick atmosphere makes it uniquely suited for heavier-than-air flight. Therefore, rather than using wheeled rovers…
Fingers of Clay
Take a mixture of a viscous liquid – like clay mud – and squeeze it between two glass plates and you’ll create a mostly-round layer of liquid. As you pry the two glass plates apart, air will push its way into that layer, forcing through the mud in a dendritic pattern. This is called the Saffman-Taylor…
“-N- Uprising”
Although Thomas Blanchard’s latest short film, “-N- Uprising”, is less overtly fluid dynamical, fluids underlie almost every aspect of it. The blossoming of flowers is often driven by osmosis and water pressure. Spiders rely on hydraulic pressure to move their limbs, and many insects first unfurl their wings by pumping hemolymph through the network of veins that lace them. Even when…
Urban Centers During Hurricanes
As the climate warms, many urban centers are facing stronger and more frequent storms. Some, like New York City, are using numerical simulations to better understand the interactions of their complicated urban geometries with hurricane force winds. Above you see a simulation showing predicted wind speeds in a Lower Eastside neighborhood. The incoming wind speed (from the…
Transporting Droplets
Transporting droplets easily and reliably is important in many microfluidic applications. While this can be done using electric fields, those fields can impact biological characteristics researchers are trying to measure. As an alternative, a group of researchers have developed the concept of “mechanowetting,” a technique that uses surface tension forces to hold droplets on a traveling wave. Now…
Oil-on-Water Impact
Although many people have studied droplet impacts over the years, there’s been remarkably little work done with oil-on-water impacts. One of the things that makes this situation different is that the oil and water are completely immiscible, which means we can see aspects of the impact process that are invisible with, say, water-on-water impacts. The animation above shows…
Ink Explosion
Sometimes beautiful flows come from simple combinations. Here the artists of Chemical Bouillon combine ink and hydrocarbons to create lovely explosions of color. Eschewing quick cuts between views, they allow us to linger and explore the flow ourselves as it changes. Differences in surface tension drive streaming flows along the surface, but there seem to be some…
Artificial Microswimmers
In a 1959 lecture entitled “There’s Plenty of Room at the Bottom”, Richard Feynman challenged scientists to create a tiny motor capable of propelling itself. Although artificial microswimmers took several more decades to develop, there are now a dozen or so successful designs being researched. The one shown above swims with no moving parts at…