#bubble pinch-off

[fuckyeahfluiddynamics]

We're all familiar with the problem of pouring a liquid from a narrow-necked bottle. (Image and research credit: L. Rohilla and A. Das; via phys.org)

[fuckyeahfluiddynamics]

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)