Perturbed breakup of gas bubbles in water: Memory, gas flow, and coalescence

TL;DR

This paper investigates how perturbations affect the singularity and dynamics of underwater bubble pinch-off, revealing the influence of gas density, shape oscillations, and boundary conditions on the breakup process.

Contribution

It provides experimental insights into symmetry-breaking effects and nonlinear outcomes during bubble pinch-off, extending understanding of perturbation impacts on singularity formation.

Findings

Gas density affects axial asymmetry and satellite bubble formation.

Azimuthal shape oscillations can be triggered by boundary conditions and nozzle shape.

Nonlinear, three-dimensional outcomes are observed with large azimuthal perturbations.

Abstract

The pinch-off of an air bubble from an underwater nozzle ends in a singularity with a remarkable sensitivity to a variety of perturbations. I report on experiments that break both the axial (i.e., vertical) and azimuthal symmetry of the singularity formation. The density of the inner gas influences the axial asymmetry of the neck near pinch-off. For denser gases, flow through the neck late in collapse changes the pinch-off dynamics. Gas density is also implicated in the formation of satellite bubbles. The azimuthal shape oscillations described by Schmidt et al., can be initiated by anisotropic boundary conditions in the liquid as well as with an asymmetric nozzle shape. I measure the n = 3 oscillatory mode, and observe the nonlinear, highly three-dimensional outcomes of pinch-off with large azimuthal perturbations. These are consistent with prior theory.