Air Bubble Entrainment In Free-surface Turbulen... -

Air entrainment is not a singular event but a multi-stage process driven by the instability of the air-water interface:

The free surfaces enclose, releasing a single or group of air bubbles into the turbulent flow. Key Drivers and Models Air Bubble Entrainment in Free-Surface Turbulen...

A surface cavity develops, reaching deeper into the water while the sides remain smooth. Air entrainment is not a singular event but

Air Bubble Entrainment in Free-Surface Turbulent Shear Flows but no air is yet trapped.

The cavity collapses due to local instabilities, often following a power-law scaling.

The free surface begins to deform slightly, but no air is yet trapped.