Coalescence regime during impingement of a liquid drop on a liquid pool

The coalescence of a drop is a common occurrence in both nature and technology, from rain formation to the production of food emulsion. However, studying the dynamics of the coalescence process of a drop is challenging due to the small time and length scales involved. Here, we investigate the coalescence dynamics of a liquid drop on a deep liquid pool at the air-liquid interface. The regime map of partial coalescence and complete coalescence phenomena is presented in terms of the pertinent governing parameters. Some key parameters are investigated in detail to analyze the dynamic behavior of the partial coalescence phenomenon quantitatively in terms of the drop tip height, kinetics of the neck radius, diameter ratio of the secondary drop to the primary drop, and the pinch-off time.