To Seal or Not To Seal

TL;DR

This study experimentally investigates splash curtain dynamics during object impact on liquid surfaces, developing an analytical model that highlights airflow velocity as the key factor in surface seal occurrence, challenging previous assumptions.

Contribution

The paper introduces a new analytical model for splash curtain behavior and identifies airflow velocity as the critical parameter for surface seal, contrasting with prior focus on impact velocity.

Findings

Identified a critical dimensionless number predicting surface seal occurrence.

Developed a scaling law for surface seal time.

Discovered airflow velocity as the dominant factor in seal formation.

Abstract

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 the interplay of cavity pressure difference, gravity, and surface tension and how they control the occurrence, or not, of 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 surface seal. This scaling indicates that the most significant parameter governing the occurrence of surface seal is the velocity of the airflow rushing into the cavity. This is in contrast to the current understanding which considers the impact velocity as the determinant parameter.