Some soap films are capable of self-healing after a solid object passes through them, as shown in the video above. The behavior is primarily dependent on Weber number–a nondimensional ratio of the film’s inertia to its surface tension. Although demonstrated for positive curvature in the video, the same behavior is observed in negatively curved soap films as well. For a look at how the behavior varies with projectile velocity and size, check out this video. (Video credit: J. Bryson, BYU Splash Lab)
Tag: science
“Kusho”
Artist Shinichi Maruyama uses photography to freeze the transient motion of fluids into water sculptures. Inertia, gravity, and surface tension are at war in each piece. Plateau-Rayleigh instabilities break long filaments of liquid into droplets that splash, collide, and reform. To see how he makes this art, check out his videos. (Photo credits: Shinichi Maruyama)
Grooving Bubbles
Here bubbles in a microchannel are subjected to an external ultrasonic acoustic field. Under the influence of this vibration, the bubbles self-organize into crystal-like structures with a fixed finite separation distance. Some bubbles cluster and contact. Some bubbles also pulsate in star-shaped vibration modes. When the external sound is turned off, the bubble crystal loses form and drifts apart. For more, see Rabaud et al. 2011. (Video credit: P. Marmottant et al.)
Microbubble Necklace
When a drop impacts a pool at very low velocity, a thin layer of air can be trapped between the drop and the pool. When this air film ruptures, a ring of microbubbles forms and expands. Multiple “bubble necklaces” can form if the film ruptures at several points. These rings travel outward until the film is completely destroyed, leaving a chandelier-like shape of microbubbles. See the phenomenon in action with one of the videos linked here. (Photo credit: S. T. Thoroddson et al.; see video at arXiv)
Leidenfrost Explosions
When a drop of water touches a very hot pan, it will skitter across the surface on a thin layer of water vapor due to the Leidenfrost effect. But what happens when another chemical is added to the droplet? Researchers find that adding a surfactant to the water droplets creates some spectacular results. As the water evaporates, the concentration of the surfactant in the droplet increases causing the surfactant to form a shell around the droplet. The pressure inside the droplet increases until the shell breaks in a miniature explosion much like the popping of popcorn. (Video credit: F. Moreau et al.)
Catastrophic Cracking from Cavitation
At your next party, you can break the bottom of a glass bottle with the palm of your hand and the power of fluid dynamics. As shown in the video above, striking the mouth of the bottle accelerates fluid at the bottom, lowering the local pressure below the vapor pressure and causing the formation of cavitation bubbles. When these bubbles collapse, they form very high temperatures and pressures for an instant, and it is this which can break the glass. (Video credit: J. Daily et al., BYU Splash Lab)
The Beauty of the Great Red Spot
Jupiter is home to one of the most famous storms in the solar system, the Great Red Spot, which Earth observations place at a minimum of 180 (Earth) years in duration. Some evidence suggests that it may have been observed by humans as early as 1665. The magnitude of such a storm is almost unimaginable. At its narrowest point, the storm is still as wide as our entire planet and observations from the Voyager crafts indicate that the storm has 250 mph winds. The scale of mixing and turbulence around the storm, seen in photographs, is stunning and beautiful. (Photo credits: NASA/Voyager 1 and Michael Benson; submitted by oneheadtoanother)
Jets from Hollows
Bubbles rising through a viscous fluid deform and interact. As they collapse into one another, the lower bubble induces a gravity-driven jet that projects upward into the higher bubble. The more elongated the bubble, the faster the jet. The same behavior is seen in the rebound of a cavity at the free surface of a liquid. The authors suggest a universal scaling law for this behavior. (Video credit: T. Seon et al.)
Viscoelastic Jets
Unlike Newtonian fluids, such as air and water, viscoelastic fluids exhibit non-uniform reactions to deformation. In this video, researchers explore the effects of this behavior when a liquid jet falls into another fluid. When fluids move past one another at different speeds in this manner, there is a shearing force which often leads to the wave-like Kelvin-Helmholtz instability between the fluids. Here we see for a variety of wavelengths how the breakdown of a Newtonian and viscoelastic jet differ. The Newtonian jets form clean lines and complicated tulip-like shapes, but the viscoelasticity of the non-Newtonian jets inhibits the growth of these instabilities, surrounding the central jet with wisps of escaping fluid. For more, see Keshavarz and McKinley. (Video credit: B. Keshavarz and G. McKinley)
Dancing Droplet Clusters
When a fluid surface is vibrated, it’s possible to bounce a droplet indefinitely on the surface without the droplet coalescing into the pool. This is because each bounce of the droplet replenishes a thin layer of air that separates the droplet and the pool. If many droplets are added to the surface, as in the video above, a clustering behavior is observed, with many droplets gathering together. There is a limit, however, to the size of the cluster based on the amplitude of vibration. If vibrational amplitudes are pushed to the point of creating Faraday waves–standing waves on the surface of the pool–then large clusters of droplets can be suspended and sustained. (Video credit: P. Cabrera-Garcia and R. Zenit; via io9; submitted by oneheadtoanother)
