Celebrating the physics of all that flows with Nicole Sharp, Ph.D.
- Profile
Stingray Wakes
This numerical simulation shows a swimming stingray and the vorticity generated by its motion. Stingrays are undulatory swimmers, meaning that the wavelength of their motion is much shorter than their body length. Manta rays, in contrast, move their fins through a wavelength longer than their body length, making them oscillatory swimmers. Observe the difference in…
Ink Diffusion
Alberto Seveso’s gorgeous high-speed photos of ink diffusing in water have a dramatic sense of texture to them. Though still delicate, the whorls of fluid seem almost solid enough to touch. Watch the edges, though, and you can see thin wisps of color and hints of instabilities. Like cream poured into coffee, these ink sculptures…
The Real Raindrop
What is the shape of a falling raindrop? Surface tension keeps only the smallest drops spherical as they fall; larger drops will tend to flatten. The very largest drops stretch and inflate with air as they fall, as shown in the image above. This shape is known as a bag and consists of a thin…
10 Years of Weather
This timelapse video captures the past 10 years’ worth of weather as seen by the GEOS-12 satellite during its service. It’s a mesmerizing look at the large-scale convective flow of Earth’s atmosphere. The prevailing winds for each region are clear from the motion of the clouds, but short-term effects are visible as well. June through…
“Pacific Light”
This lovely video from Ruslan Khasanov showcases the beautiful interplay of surface tension, diffusion, and immiscibility in common fluids. With soy sauce, oil, ink, soap, and a little gasoline, he creates a mesmerizing world of color and motion. It’s a great reminder of the wonders that populate our daily lives, if we just look closely…
Why Honeycomb is Hexagonal
The regular hexagonal structure of honeycomb may owe more to fluid dynamics than the careful engineering of the bees that build it. Observations indicate that honeycomb cells start out circular and become hexagonal as the bees continue building. Both experiments and models show that an array of circular cells can transform into hexagons due to…
Ski Jumping Aerodynamics
Last summer we featured fluid dynamics in the Summer Olympics and there’s more to come for Sochi. Winter athletes like ski jumper Sarah Hendrickson are hard at work preparing, which can include time in wind tunnels, as shown here. There are two main diagnostics in tests like these: drag measurements and smoke visualization. The board…
Shocking Instabilities
The Richtmyer-Meshkov (RM) instability occurs when the interface between two fluids of different density is impulsively accelerated – usually by the passage of a shock wave. The image above shows a thin layer of gaseous sulfur hexafluoride embedded in air. Each vertical line, from left to right, shows the distortion of the two fluids at…
Evaporating Drops
When still drops evaporate from a surface, they do so in several phases, as illustrated in the video above. Initially, the drop forms a spherical cap. At this point the velocity within the droplet is so small that it is difficult to resolve, but particles within the drop move outward toward the contact line. As…
Fluids Round-up – 24 August 2013
Fluids round-up time! Here are your latest fluids links to check out: One of the great fundamental questions of life is, of course: what is the airspeed velocity of an unladen swallow? Jonathan Corum explains how to use fluid dynamics to estimate the answer. (submitted by Andrew C) Sound and acoustics play a big role in fluid…