When a water drop strikes a pool, it can form a cavity in the free surface that will rebound into a jet. If a well-timed second drop hits that jet at the height of its rebound, the impact creates an umbrella-like sheet like the one seen here. The thin liquid sheet expands outward from the point of impact, its rim thickening and ejecting tiny filaments and droplets as surface tension causes a Plateau-Rayleigh-type instability. Tiny capillary waves–ripples–gather near the rim, an echo of the impact between the jet and the second drop. All of this occurs in less than the blink of an eye, but with high-speed video and perfectly-timed photography, we can capture the beauty of these everyday phenomena. (Photo credit: H. Westum)
Category: Art
“Orchid”
Artist Fabian Oefner enjoys capturing both art and science in his work. In his latest series, “Orchid”, the blossom-like images are the result of splashes. He layered multiple colors of paint, ending with a top layer of black or white, then dropped a sphere into the paint. The images show how the colors mix and rebound, a delicate splash crown seen from above. The liquid sheet thickens at the rim and breaks up into ligaments from the instability of the crown’s edge. It makes for a remarkable demonstration of the effects of momentum and surface tension. Several of Oefner’s previous collections have appeared on FYFD (1, 2, 3). (Photo credit: F. Oefner)
Liquid Sculptures
[original media no longer available]
Water sculptures–a marriage of liquids, photography, and timing–are spectacular form of fluid dynamics as art. Artist Markus Reugels is a master of the form. This video captures the life and death of such water sculptures at 2,000 fps, beginning with the fall of the initial blue droplet. The droplet’s impact causes a rebounding Worthington jet, which reaches its pinnacle just as a second droplet strikes. The impact spreads into an umbrella-like skirt consisting of a thin, expanding liquid sheet with a thicker rim. The rim itself is unstable, breaking into regularly spaced filaments and tiny satellite droplets that shoot outward before the entire structure collapses into the pool. One especially cool aspect of watching this in video is seeing how the blue dye from each droplet spreads as the water splashes and rebounds. You can see the set-up Reugels uses for his photography here. (Video credit: M. Reugels and L. Lehner)
“Supermajor”
In Matt Kenyon’s “Supermajor,” oil appears to flow upward against gravity from a puddle into a can. This optical illusion is a stroboscopic effect similar to the one that makes car wheels seem to rotate backwards. The human eye and brain can be tricked into seeing the stream of oil as being suspended or even moving backwards by changing the flicker of the lighting relative to the rate at which the drops fall. If you watch the videos carefully, the pedestal is vibrating, which imparts a specific frequency to the falling drops. Combine this with a light that flickers at a slightly different frequency than that of the vibration and you can make the stream of drops appear to move up or down. It’s a helpful way to trick the brain into freezing fluid motion we would normally be unable to appreciate without high-speed cameras. (Video credit: Science Gallery; exhibit credit: Matt Kenyon; submitted by jshoer)
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 are short-lived. Some of his works are available as prints or wallpapers (zip file). (Photo credit: Alberto Seveso)
“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 enough to see them. (Video credit: R. Khasanov; via Wired; submitted by Trevor)
“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 and large contact angle of the puddle’s rim. The oils mixed in float on top, creating patterns of foam that visualize the swirling motions of the fluid as the vortex pulls it in. (Video credit and submission by: A. Hall)
“Liquid Jewel”
Just a reminder that today is your last chance to participate in our reader survey. If you haven’t had a chance yet to fill it out, please do. The data are very important to us, not just for this site, but for improving science outreach online in general. Thank to those who have filled out the survey and especially those who left suggestions. You guys have some great ideas!
Today’s image is from artist Fabian Oefner’s “Liquid Jewel” series, featuring paint-filled balloons moments after rupture. Oefner has several series displaying physical forces as visual media, including the previously featured “Black Hole” and “Millefiori” photos. (Photo credit: F. Oefner)
“Adrift”
Sometimes the time scales of a flow can mask its similarities to other flows. Simon Christen’s “Adrift,” a video of timelapsed fog in the San Francisco Bay area, shows just how these low clouds undulate and flow over the land the way a stream of water flows over and around stones. From the flow of gases in a stellar nursery down to the channels of a lab-on-a-chip, the same physics governs fluids everywhere, and there are always similarities to be found and exploited in our efforts to understand and explain fluid dynamics. (Video credit: S. Christen; via io9)
The Colors of Soap
The brilliant and beautiful colors of a bubble are directly related the the thickness of the soap film surrounding it. When light shines on the soap film, some rays are reflected from the upper surface of the film, while others are refracted through the film and reflect off its lower surface. These reflected rays have different phase shifts and their interference is what causes the colors we observe. The color patterns themselves reveal the interior flow of the soap film, in which gravity tries to thin the film and surface tension tries to distribute the film evenly. (Photo credit: R. Kelly, A. Fish, D. Schwichtenberg, N. Travers, G. Seese)
