Celebrating the physics of all that flows with Nicole Sharp, Ph.D.
- Profile
Ferrofluid Drop
A drop of ferrofluid is shaped by seven small circular magnets sitting beneath the glass and paper. Ferrofluids are made up of nanoscale ferromagnetic particles suspended in a carrier liquid. Under the influence of magnetic fields, they can take on fantastic shapes, including sharp-tipped droplets and labyrinthine mazes. This image is taken from the National…
Boiling Without Bubbles
Water droplets sprinkled on a sufficiently hot frying pan will skitter and skate across the surface on a thin layer of vapor due to the Leidenfrost effect. When a solid object is much warmer than a liquid’s boiling temperature, the surface is surrounded by a vapor cloud until the solid cools to the point that…
The Veil Nebula
There is no grander scale for the observation of fluid dynamics than that of the astronomical. Here Hubble astronomers discuss the formation of the Veil Nebula, a supernova remnant formed some 5,000-10,000 years ago. Wisps of gas and plasma remain, creating stunning astronomical landscapes that are the result of shock waves, turbulence, diffusion, and other…
Liquid Logic Gates
Researchers have built logic gates–a physical implementation of Boolean logic–using droplets on a superhydrophobic surface. The video above demonstrates their flip-flop memory gate. Incoming droplets travel on a single track, striking a stationary “memory droplet” which then goes into one of the two output tracks according to its memory state. The memory state of the…
Chronoscapes
Exeter University artist-in-residence Pery Burge uses ink, water, soap films, and other fluids to create her spectacular “artistic flow visualization”. Looking closely, one sees the influence of bubbles, vortices, diffusion, and many fluid instabilities, all combined to create psychedelic and dream-like landscapes. For more on her work and additional galleries, see her website Chronoscapes. (Photo credit: Pery…
Wingtip Vortices
Any finite length wing produces wingtip vortices–potentially intense regions of rotational flow downstream of the wing’s ends. These vortices are associated both with the production of lift on the wing and with unavoidable induced drag. The tabletop demonstration above shows the region of the vortices’ influence and how strong the rotation is there. Note also…
The Supersonic Plonk
Everyone knows the familiar plonk of a stone falling into a pond but few realize the complexity of the physics. When a solid object falls into a pool, a sheet of liquid, the crown splash, is sent upward. Simultaneously, the object pulls a cavity of air down with it. As the water moves inward, this…
Bouncing Off
A water droplet falling onto a superhydrophobic surface will rebound and bounce without wetting the surface. Capillary and internal waves reflect in the drop until it comes to rest at a high contact angle, formed at the boundary where the liquid, solid, and air meet. Such surfaces can have interesting interactions with water, as when…
Didgeridoo Soap Bubble
This high-speed video shows a soap bubble being blown via didgeridoo, a wind instrument developed by the Indigenous Australians. The oscillations of the capillary waves on the surface of the bubble vary with the frequency of note being played. High frequency notes excite small wavelengths, whereas lower notes create large wavelength oscillations. For more fun,…
Using Flow Viz for Optimization
Flow visualization is a powerful design tool for engineers. When Google was interested in determining optimal configurations for their heliostat array, they turned to NASA Ames’ water tunnel facility to test upstream barriers to deflect flow off the heliostats. In each photo, flow is from left to right and fluorescent dye is used to mark…