The regime of large bubble entrapment during a single drop impact on a liquid pool

Abstract

The present study focuses on the identification of the large bubble entrapment regime on the V-D map and on the We-Fr map together with the detailed analysis of the mechanism of large bubble entrapment. The sequential large and small bubble entrapment previously found by Wang, Kuan, and Tsai [“Do we understand the bubble formation by a single drop impacting upon liquid surface?,” Phys. Fluids 25, 101702 (2013)] has been observed in this investigation. Large bubble entrapment is observed only for prolate-shaped drops. Prolate shaped drops bring about deeper penetration of the vortex ring into the pool. The emergence of an ejecta sheet that leads to lamella prevents the penetration of the vortex ring and thus prevents the large bubble entrapment. The entrapment of a large bubble is always accompanied by an inward jet and an upward jet. The inward jet penetrates through the bubble and deforms the bubble shape. A thorough parametric study has been conducted numerically and experimentally on the crater dynamics and its dependence on the initial condition of the drop at the instance of impact.