On a recent trip to G.E., the Slow Mo Guys used their high-speed camera to capture some great footage of dyed water on a superhydrophobic surface. Upon impact, the water streams spread outward, flat except for a crownlike rim around the edges. Then, because air trapped between the liquid and the superhydrophobic solid prevents the liquid from wetting the surface, surface tension pulls the water back together. If this were a droplet rather than a stream, it would rebound off the surface at this point. Instead, the jet breaks up into droplets that scatter and skitter across the surface. There’s footage of smaller droplets bouncing and rebounding, too. Superhydrophobic surfaces aren’t the only way to generate this behavior, though; the same rebounding is found for very hot substrates due to the Leidenfrost effect and very cold substrates due to sublimation. As a bonus, the video includes ferrofluids at high-speed, too. (Video credit: The Slow Mo Guys/G.E.)
Whenever a hollow cavity forms at the surface of a liquid, the cavity’s collapse generates a jet—a rising, high-speed column of liquid. The composite images above show snapshots of the process, from the moment of the cavity’s greatest depth to the peak of the jet. The top row of images shows water, and the bottom row contains a fluid 800 times more viscous than water. The added viscosity both smooths the geometry of the process and slows the jet down, yet strong similarities clearly remain. Focusing on similarities in fluid flows across a range of variables, like viscosity, is key to building mathematical models of fluid behavior. Once developed, these models can help predict behaviors for a wide range of flows without requiring extensive calculation or experimentation. (Image credit: E. Ghabache et al.)
Transience is the Japanese calligraphy work with dynamic color changes. The scene where the letter colors are changing from moment to moment can give affluent dynamism and feeling of vitality of calligraphy to viewers, and at the same time, it can express stream of time. Calligraphy is integrated with technology and materials seamlessly and Transience is produced to show ever-changing aesthetics fermented in Japan.
In order to change letter colors on paper, we developed our original chromogenic mechanism from functional inks and conductive materials. For producing the chromogenic technology suitable for paper, we examined ink materials repeatedly, and as a result we realized the expression where calligraphy harmonizes with computer.
Since ancient times, human beings have expressed beauty by linking paper technologies, techniques and cultures intricately. As paper materiality and letter images are united with technologies, a new dynamism will be created on paper.
Two interesting sets of clouds are featured in this satellite photo of the Canary Islands and the coast of Africa. In the upper part of the picture, closed cell stratocumulus clouds cover the ocean. As the wind drives these clouds over the islands, their pattern is disturbed by mountains that force the lower layers of air up and around, forming von Karman vortices and wakes that mingle and twist the cloud patterns to the south of the islands. (Photo credit: European Space Agency; via Wired)
Flow visualization in a water tunnel shows what the flow around a line of traffic looks like. Note the progressively more turbulent flow around each car as it sits in the wake of the car before it. Turbulent flow is usually associated with increased drag forces, but because turbulence can actually help prevent flow separation it is sometimes desirable as a method for decreasing drag. In the case of these cars drafting on one another, it is clear that the cars further back in the line cause less effect on the fluid—and thus have less drag to overcome—than the front car. (Photo credit: Rob Bulmahn)