Celebrating the physics of all that flows with Nicole Sharp, Ph.D.
- Profile
Navigating the Interface
Walking on water may be the stuff of legend at human scales, but it’s a fact of everyday life for many smaller species. Waxy, hydrophobic coatings typically make such insects’ points of contact (feet, legs, etc.) water-repellent, and their light weight can be supported by surface tension. Navigating the interface between air and water is…
Fluids Round-up – 11 August 2013
Time for another fluids round-up! Here are your links: Back in January 1919, a five-story-high metal tank full of molasses broke and released a wave of viscous non-Newtonian fluid through Boston’s North End. Scientific American examines the physics of the Great Molasses Flood, including how to swim in molasses. If you can imagine what it’s like…
Contaminants Flowing Uphill
Here’s an example of some baffling fluid dynamics. Researchers have found that, when pouring a fluid from one container into a lower one containing a fluid with floating particulates, it’s possible for the floating particles to travel upstream against gravity and the flow. The phenomenon is driven by surface tension. The particulates floating in the…
Convection on the Sun
New photographs showing ultra-fine structure in the sun’s chromosphere and photosphere have been released. They offer a fascinating view into the magnetohydrodynamics of the sun, where the fluid behaviors of plasma are constantly modified by the sun’s magnetic field. The left image shows fine-scale magnetic loops rooted in the photosphere, while the right image shows…
Bubbles With Tails
In water and other Newtonian fluids, a rising bubble is typically spherical, but for non-Newtonian fluids things are a different story. In non-Newtonian fluids the viscosity–the fluid’s resistance to deformation–is dependent on the shear rate and history–how and how much deformation is being applied. For rising bubbles, this can mean a teardrop shape or even…
Bouncing in Lockstep
Droplets of silicone oil bounce on a pool of the same thanks to the vibration provided by a loudspeaker. Each droplet’s bounce causes ripples in the pool and the interference between these ripples fixes the droplets in lockstep with one another. As long as the vibration continues to feed the thin layer of air that…
Flow Over a Delta Wing
Fluorescent dye illuminated by laser light shows the formation and structure of vortices on a delta wing. A vortex rolls up along each leading edge, helping to generate lift on the triangular wing. As the vortices leave the wing, their structure becomes even more complicated, full of lacy wisps of vorticity that interact. Note how,…
Self-Assembling Ferrofluids
Ferrofluids–colloidal suspensions made up of ferromagnetic nanoparticles and a carrier liquid–are known for their interesting and sometimes bizarre behaviors due to magnetic fields. The video above shows how, when subjected to an increasing magnetic field, a single droplet of a ferrofluid on a superhydrophobic surface will split into several droplets. The process is called static…
“Perpetual Puddle Vortex Experiment”
Anthony Hall’s “Perpetual Puddle Vortex Experiment” is an intriguing display of several physical mechanisms. What looks like a puddle is actually a vortex constantly sucking fluid down a hole in the table. The liquid is re-circulated into the puddle so it never disappears. The table itself is treated to be hydrophobic, causing the distinctive curvature…
Instability: Dense Over Light
Here on Earth, placing a dense layer of fluid atop a less dense layer is unstable. Specifically, the situation causes the interface between the two fluids to break down in what is known as the Rayleigh-Taylor instability.The video above shows a 2D numerical simulation of this breakdown, with the darker, denser fluid on top. The…