Capillary driven fragmentation of large gas bubbles in turbulence

TL;DR

This study investigates how large gas bubbles break into smaller ones in turbulent conditions, revealing a capillary-driven fragmentation process that follows a specific power law scaling.

Contribution

It combines experimental and numerical methods to identify a capillary-driven break-up mechanism and a power law scaling for small bubble sizes in turbulence.

Findings

Small bubble size distribution follows a 3/2 power law scaling.

Break-up times scale with bubble diameter to the 3/2.

Capillary effects dominate the break-up of small bubbles.

Abstract

The bubble size distribution below a breaking wave is of paramount interest when quantifying mass exchanges between the atmosphere and oceans. Mass fluxes at the interface are driven by bubbles that are small compared to the Hinze scale $d_h$, the critical size below which bubbles are stable, even though individually these are negligible in volume. Combining experimental and numerical approaches, we report a power law scaling 3/2 of the diameter of small bubble size distribution, for sufficiently large separation of scales between the injection size and the Hinze scale. From an analysis of individual bubble break-up events, we show that break-ups generating small bubbles are driven by capillary effects, and that their break-up time scales with the diameter to the 3/2, which physically explains the sub-Hinze scaling observed.