We study drop impact on a deep pool of the same fluid, with an emphasis on the air layer trapped under the droplets from its formation to its rupture. The penetration velocity of the air layer at a very short time scale prior to its rupture is shown, using an energy argument and experimental verification, to be one-half of the impact velocity. We then deduce the dependence of the rupture position on the liquid viscosity and the impact velocity. We show that the volume of the resulting air bubbles can be related to both those resulting from droplets impacting on solid surfaces and those resulting from rigid spheres impacting on liquid surfaces.

While the dynamics of complete wetting has been widely studied for liquids, the way a gas spreads on a solid is by far less known. We report here the events following the rise of a millimeter-size air bubble towards a textured material immersed in water and covered by a thin plastron of air. Bubbles contact the material either directly at the end of the rise, or after a few rebounds, which affects the initial shape of the bubble and the resulting dynamics of contact. Then, air spreads on the material, owing to surface tension and later buoyance, which tends to flatten further the bubble. The corresponding dynamics are shown to result from the inertial resistance of water, which explains how spreading bubbles reach centimeter sizes in typically 10 ms.