To seal or not to seal: The closure dynamics of a splash curtain

When an object impacts the free surface of a liquid, it ejects a splash curtain upwards and creates an air cavity below the free surface. As the object descends into the liquid, the air cavity eventually closes under the action of hydrostatic pressure (deep seal). In contrast, the surface curtain may splash outwards or dome over and close, creating a surface seal. In this paper, we experimentally investigate how the splash curtain dynamics are governed by cavity pressure difference, gravity, and surface tension, and how their interplay controls the occurrence, or not, of the surface seal. Based on the experimental observations and measurements, we develop an analytical model to describe the trajectory and dynamics of the splash curtain. The model enables us to reveal the scaling relationship for the dimensionless surface seal time and discover the existence of a critical dimensionless number that predicts the occurrence of the surface seal. This scaling indicates that the most significant parameter governing the occurrence of a surface seal is the velocity of the airflow rushing into the cavity, which is in contrast to the current understanding that considers the impact velocity as the determinant parameter.