Delayed bubble entrapment during the drop impact on a bounded liquid bath

Numerical researches on the impact of a drop onto a bounded liquid bath are carried out using GERRIS code. A particular region of delayed bubble entrapment is presented. During a typical impact, a first crater, a liquid column and a second crater appear successively. It is found that gravity, restricted bath diameter and impact velocity play important roles in the whole process. With a proper bath diameter, the outward propagating waves at the liquid surface can be reflected back to the center in time and lead to a liquid column. The delayed bubble can be entrapped when the second crater is deep enough. When the bounded liquid bath is too narrow or too broad, no delayed bubble is formed, as the liquid column breaks before the second crater becomes deep enough. The mechanism of delayed bubble entrapment is explained through surface profiles and velocity fields.