Celebrating the physics of all that flows with Nicole Sharp, Ph.D.
- Profile
Mushrooms Make Their Own Breeze
Plants and other non-motile organisms have developed some clever methods to disperse their seeds and spores for reproduction. Some plants use vortex rings for dispersal; others make their seeds aerodynamic. Low ground-dwellers like mushrooms must contend with a lack of wind to lift their spores and carry them away. Instead, they use evaporative cooling to…
Hovering Hummingbirds
Hummingbirds are incredible flyers, especially when it comes to hovering. To hover stationary and stable enough to feed, the hummingbird’s flapping pattern not only has to generate enough lift, or vertical force, to counteract their weight, but the bird must balance any forward or backward forces generated during flapping. As you can see in the animations…
Coffee-Making in Space
In this video, Kjell Lindgren demonstrates his technique for making coffee aboard the Space Station. Astronauts usually drink coffee reconstituted from powder, or, on special occasions, enjoy a beverage from their special espresso machine. But Lindgren uses a pour-over method by attaching a pod of coffee grounds to the underside of a Capillary Beverage Experiment…
Eulerian vs. Lagrangian
When I first studied fluid dynamics, one of the concepts I struggled with was that of Eulerian and Lagrangian reference frames. Essentially, these are just two different perspectives you can view the fluid from. Physics is the same in both, but mathematically, you approach them differently. In the Eulerian perspective one sits at a location…
Martian Viscous Flow
These images from the Mars Reconnaissance Orbiter show what are called viscous flow features. They are the Martian equivalent of glacial flow. Such features are typically found in Mars’ mid-latitudes. Ground-penetrating radar studies of Mars have shown that some of these features contain water ice covered in a protective layer of rock and dust, making…
Rotating Jet
This photo, one of the winners of the Engineering and Physical Sciences Research Council’s (EPSRC) annual photography contest, shows a rotating viscoelastic jet. Rotating liquid jets are common to many manufacturing processes, and their sometimes-wild appearance comes from a balance of gravitational forces and centrifugal force against surface tension. But because this fluid contains a small…
Filter-Feeding Mantas
Large filter-feeders like the manta ray face the interesting challenge of obtaining enough small particulates like plankton to sustain an animal the size of a car. They do this through what is known as ram filter-feeding, essentially swimming open-mouthed through food-laden waters, filtering out the food, and releasing the water through their gills. Their internal…
Wrinkling Fluids
What you see here is a viscous drop falling into a less viscous fluid. Shear forces between the drop and the surrounding fluid cause the drop to quickly deform into a shape like an upside-down mushroom as it descends. The cap forms a vortex ring that curls the viscous fluid back on itself. As it…
Singing Sand Dunes
Reports of singing sand dunes date at least as far back as 800 C.E. Strange as it sounds, about forty sites around the world have been associated with this phenomenon, in which avalanches of sand grains on the outer surface of the dune cause a deep, booming hum for up to several minutes. As you…
Review: “Life in Moving Fluids”
If you liked the prairie dog post earlier this week and you’re interested in more examples of biological fluid dynamics, you may enjoy Steven Vogel’s “Life in Moving Fluids”. I’m often asked for suggestions of readable textbooks for those who want an introduction to fluid dynamics, and this book is a great option. It addresses…