When does a surface seal cavity really seal?

The pervasive sequence characterizing water entry - impact, splash formation, cavity seal, cavity collapse - has been meticulously investigated, particularly at low impact speed (~1-10 m/s). The splash plays a crucial role in determining the regime of cavity formation, either remaining open long enough to enable quasi-static, shallow or deep seals, or closing above the free-surface and initiating a surface seal. At higher speeds, up to Mach 1 in air (~10-300 m/s), cavities have been largely categorized as surface seals. However, the observation of subtle changes in splash and sub-surface phenomena over this speed range raises the question of when and how the cavity actually seals. At low speeds, the splash domes over above the surface and seals the cavity. Here we show that at high speeds the splash root buckles and breaks, allowing gas inflow through a conical gas curtain that persists after the cavity has pulled away from the free surface. Our findings provide insight into cavity closure mechanics over a wide speed range with implications for the total mass of gas that ends up in the cavity.