Celebrating the physics of all that flows with Nicole Sharp, Ph.D.
- Profile
Jet Collisions
When two jets of liquid collide, they form a sheet of fluid. As the speeds of the jets change, the sheet can become unstable, forming a set of liquid ligaments and droplets that look like a fish’s bones. This is shown in the video above. For purposes of orienting yourself, flow in the video is…
Soap Bubbles Bursting
To the human eye, the burst of a soap bubble appears complete and instantaneous, but high-speed video reveals the directionality of the process. Surface tension is responsible for the spherical shape of the bubble, and, when the bubble is pierced, surface tension is broken, causing the soap film that was the bubble to contract like…
Stalling a Wing
At small angles of attack, air flows smoothly around an airfoil, providing lifting force through the difference in pressure across the top and bottom of the airfoil. As the angle of attack increases, the lift produced by the airfoil increases as well but only to a point. Increasing the angle of attack also increases the…
Reader Question: Drafting in Cycling
jonesmartinez asks: As a cyclist, I’m curious about drafting. How fast do I need to be going for there to be a measurable benefit? Additionally, often in a time trial a single rider is often followed by the team car and I’ve heard the rider can be pushed by the air around the team car.…
Martian Lava Coils
NASA’s HiRISE spacecraft has sent back images of lava coils left on the surface of Mars. These features form when lava flows of different speeds move past one another; they’re essentially Kelvin-Helmholtz waves–like the ones often seen in clouds–in the lava flow that have solidified into solid rock! On Earth these coils appear about a…
Why Walking with Coffee is Tough
Almost everyone is familiar with the problem of coffee or tea sloshing over the sides of a mug as one walks, but this may be the first time researchers have systematically studied the problem. The results show that the typical frequency of the human stride closely matches the natural frequency for back-and-forth sloshing of a…
Egg Spinning
Spin a hard boiled egg in a puddle of milk and you get a sprinkler. But how? The science starts at the surface. When the egg spins, the fluid touching its surface is dragged along due to friction, and, because of the fluid’s viscosity, other parts of the fluid will also be spun. Dynamics tells…
“Compressed” Outtakes
Bubbles, viscosity, diffusion, capillary action, and ferrofluids all feature in the artistic experiments of Kim Pimmel. Be sure to check out his previous film featured here. (Video credit: Kim Pimmel)
Moving Droplets with Electric Fields
Many microfluidic devices employ techniques that manipulate droplet motion for applications like sorting, manufacturing, or precisely controlling chemical reactions at a small scale. The video above shows the oscillations of a droplet on an inclined surface as it is perturbed with an electric field. (Video credit and submission: K. Nichols)
The Pitch Drop Experiment
Sometimes everyday materials are more fluid than they seem. In 1927, Professor Thomas Parnell of the University of Queensland started what is now the longest continuously running laboratory experiment when he filled a sealed glass funnel with a sample of heated tar pitch. After allowing 3 years for the pitch to settle, the funnel’s stem…