Liquid acrobatics

TL;DR

This paper explores the fluid dynamics of injecting gas into shallow liquids, revealing cyclical jet formations and droplet behaviors through high-speed imaging, highlighting complex interfacial phenomena.

Contribution

It presents novel observations of cyclical jet eruptions and droplet trajectories in gas-liquid interactions, documented via high-speed camera footage.

Findings

Cyclical jets erupt from the air-liquid interface.

Droplets follow parabolic trajectories and bounce before coalescing.

Jet shape and timing are remarkably consistent.

Abstract

We experiment with injecting a continuous stream of gas into a shallow liquid, similar to how one might blow into a straw placed at the bottom of a near-empty drink. By varying the angle of the straw (here a metal needle), we observe a variety of dynamics, which we film using a high-speed camera. Most noteworthy is an intermediate regime in which cyclical jets erupt from the air-liquid interface and breakup into air-born droplets. These droplets trace out a parabolic trajectory and bounce on the air-liquid interface before eventually coalescing. The shape of each jet, as well as the time between jets, is remarkably similar and leads to droplets with nearly identical trajectories. The following article accompanies the linked fluid dynamics video submitted to the Gallery of Fluid Motion in 2008.