Celebrating the physics of all that flows with Nicole Sharp, Ph.D.
- Profile
Oil in Alcohol
In this video two droplets of oil fall through a bath of isopropyl alcohol. The oil is denser than alcohol, and the two fluids are miscible. The velocity and density gradients where the two fluids meet generate hydrodynamic instabilities that create the distinctive patterns seen in the falling drops. (Video credit: BYU Splash Lab)
Mussels
In this video, schlieren imaging is used to make visible the flow field around a mussel. Mussels are filter-feeders, drawing nearby water in to obtain their food and expelling the unneeded fluid once they’ve gathered the plankton they eat. Normally this process is invisible to the naked eye, but schlieren imaging reveals changes in density…
Sally Ride
Today FYFD takes a brief aside from fluid dynamics to mark the passing of Sally Ride, the first U.S. woman to travel to space. A physicist by training, Ride served as a mission specialist on STS-7 and STS-41G, shuttle missions that included deploying satellites as well as conducting scientific experiments. After her career with NASA,…
How Maple Seeds Fly
Maple tree seeds flutter and spin as they descend. The above video, which shows flow visualization of a freely falling seed, demonstrates that the so-called helicopter seed’s autorotation creates a vortex along the leading edge. Watch as the seed’s “wing” sweeps through and you will notice the vortex along the upper surface. This leading edge vortex…
Turing Patterns
Turing patterns form as a result of a particular kind of chemical reaction: a reaction-diffusion system. It consists of an activator chemical capable of making more of itself, and an inhibitor chemical which slows the production of the activator as well as a mechanism for diffusing the chemicals. Although Turing’s original work was theoretical in…
Vibrating Mercury
A drop of mercury on a vibrating teflon surface assumes various mode shapes as the amplitude and frequency of oscillation are changed. Note the geometry and symmetry of the mode shapes. Near the end of the movie, the mercury oscillates chaotically and all symmetry and pattern is broken. (Because mercury is toxic, do not try…
Liquid Pearls
Researchers create liquid pearls–a liquid droplet surrounded by a gel-like exterior–by dropping the fluid through a special bath. The initial droplet contains a mixture of the liquid core and an alginate solution. When the drop falls through a bath containing calcium ions, the alginate turns into a hydrogel shell around the liquid core. In order…
Titan’s Vortex
The timelapse animation above shows a swirling vortex above the south pole of Saturn’s moon Titan. It completes a full rotation in about nine hours, significantly quicker than the 16-day rotation of the moon. The vortex appears to demonstrate open cell convection, in which air sinks at the center of the cell and and rises…
Paper Marbling
[original media no longer available] Suminagashi, the Japanese art of “floating ink”, is one of many methods historically used for paper marbling. In it, a shallow layer of water or other viscous fluid serve as a medium for drops of ink that diffuse across the fluid surface and are manipulated with straws, brushes, or other…
Flapping Wakes
As a flapping object moves through a fluid, many patterns of vortices can form in its wake. The familiar von Karman vortex street, so often seen in clouds or behind cylinders, is only the beginning. In the photo above, a symmetric foil flaps in a vertical soap film; as the amplitude and frequency of the oscillation varies,…