Origin of the sub-Hinze scale bubble production in turbulence

In turbulent flow, bubble breaking generates a broad distribution of sizes $d$, which scales as $d^{-10/3}$ and holds down to the Hinze scale $d_h$, the size separation between stable ($dd_h$). The sub-Hinze bubble distribution remains poorly understood, while it plays important roles in many practical situations, such as low solubility gas fluxes at the ocean-atmosphere interface. Combining experimental and numerical approaches, we report a power law scaling $d^{-3/2}$ for the small bubble size distribution, for sufficiently large separation of scales between the injection size and the Hinze scale. From an analysis of individual events, we show that break-up events generating small bubbles are driven by capillary effects, and that their break-up time scales as $d^{3/2}$, which physically explains the sub-Hinze scaling observed.