The role of solid surface in bubble formation and detachment at a submerged orifice

TL;DR

This paper investigates how solid surface wettability influences bubble formation and detachment at submerged orifices, providing a quantitative explanation and proposing an alternative bubble pinch-off mechanism.

Contribution

It redefines capillary and adhesive forces at the orifice edge, establishing a quantitative relation between bubble volume and surface wettability, and introduces a new mechanism for bubble pinch-off.

Findings

Bubble size varies with surface wettability.

A quantitative model links bubble volume to wettability.

An alternative bubble pinch-off mechanism is proposed.

Abstract

Bubble formation and detachment at a submerged orifice exists widely in both daily life and academic research, and the influence of solid surface on bubble formation and detachment has also been extensively investigated. For example, it has been observed that the bubble on a hydrophobic surface is larger than the one on a hydrophilic surface. However, this phenomenon is not sufficiently explained in existing literature. To explain it, we redefine the capillary force at the orifice edge and the adhesive force between bubble and solid. Subsequently, we are able to establish an approach that quantitatively explains the relation between bubble volume and surface wettability. In addition, we also suggest an alternative mechanism of bubble pinch-off. In our opinion, the formation of bubble neck during pinch-off may be due to three-phase equilibrium at the orifice edge, and the breakup of bubble neck may result from the stretching action of the upward buoyancy force and the downward capillary force.