A fountain of droplets

TL;DR

This study investigates how oscillating an inverted vessel in silicone oil creates surface waves and droplet ejections, revealing the influence of vessel shape and oscillation amplitude on wave patterns and droplet formation.

Contribution

It introduces the effect of vessel shape and oscillation parameters on wave dynamics and droplet ejection in an oscillating air/oil interface system.

Findings

Wave amplitude increases with oscillation amplitude.

Vessel shape influences the air/oil meniscus and wave patterns.

Droplet ejection occurs at each oscillation cycle, with more complex ejections at higher amplitudes.

Abstract

A vessel is plunged upside down into a pool of 50 cSt silicone oil. An air bell is then created. This bell is vertically shaken at 60 Hz that leads to the oscillation of the air/oil interface. The edges of the immersed vessel generate surface waves that propagate towards the center of the bell. When the amplitude of the oscillation increases, wave amplitude increases. We study the influence of the angle between successive sides on the wave patterns. Two kinds of vessel have been studied: a triangular and a square prism. The shape of the air/oil meniscus depends on the angle between the sides of the considered prism. As the amplitude of the oscillation is increased, the triple line, which is the contact line between the solid and the air/oil interface, moves up and down. Above a given acceleration that depends on the immersion depth and on the shape vessel, wave goes under the corner edge of the bell. During the oscillation, the wave generates at the edges presents a singularity that leads eventually to a jet and a drop ejection. A drop is ejected at each oscillation. More complicated ejection can be produced with further increase of the amplitude. This is a sample arXiv article illustrating the use of fluid dynamics videos.