Geyser Sculptures

In the remote landscape of Tajikistan, photographer Øystein Sture Aspelund discovered a small geyser near a high-altitude lake. With a fast shutter, he "froze" the shapes of the eruption, capturing bubbly columns, mushrooms, and splashes. (Image credit: Ø. Aspelund; via Colossal) Read the full article

Bubbles in industrial applications are often more complicated than a simple pocket of air surrounded by water. Here researchers investigate the formation of an air bubble coated in oil before it rises through water. (Image and research credit: B. Ji et al.)

The dripping of a faucet and the break-up of a jet into droplets is universal. That means that the forces -- the inertia of the fluid, the capillary forces governed by surface tension, and the viscous dissipation -- balance in such a way that the initial conditions of the jet -- its size, speed, etc. -- don’t matter to the process of break-up. 

We’d expect that the inverse situation -- the breakup of a gas into bubbles in a liquid -- would be similarly universal, but it’s not. When unconfined bubbles pinch off, the way they do so is heavily influenced by initial conditions. But that changes, according to a new study, if you confine the gas to a liquid-filled tube before pinch-off. Confinement forces a different balance between viscous and capillary effects, one which effectively erases the initial conditions of the flow and restores universality to the pinch-off process. (Image and research credit: A. Pahlavan et al.; via phys.org)

Most people know that throwing water into hot oil is a bad idea. But, as dramatic as the results can be, the boiling of a water droplet submerged in oil is remarkably beautiful, as seen in the animations above. The initial water droplet expands as it shifts from liquid to vapor (top). At a critical volume, the expansion occurs explosively (middle), causing the bubble to overexpand relative to the pressure of the surrounding fluid. The higher pressure of the oil around it collapses the drop, which then re-expands, creating the cycle we see in the final two animations. This oscillation triggers a Rayleigh-Taylor type instability along the bubble’s interface, causing the surface corrugations observed. The vapor bubble will continue to rise through the oil, eventually breaking the surface and scattering hot oil droplets.  (Image credits: R. Zenit, source)