Fundamental characteristics of secondary drops produced by early splash during single-drop impingement onto a thick liquid film

Abstract

Basic features of early-splash droplets produced during single-drop impact onto a quiescent liquid film were explored experimentally using water and three aqueous solutions of glycerol at different concentrations as the test liquids. It was found that the time from the contact of primary drop with a liquid film is a crucial parameter in determining the size, ejection velocity, and ejection angle of secondary drops. It was also shown that the time period for the early splash to occur, the total number of secondary drops, and the number of secondary drops produced per unit time are dependent primarily on the impact Weber number. From the experimental data accumulated in this work, dimensionless correlations were developed for these quantities. These correlations can be used to calculate various quantities such as the total mass, total surface area, and total kinetic energy of the secondary drops. As a typical example, the total mass of the secondary drops was calculated to explore its dependence on the Weber and Ohnesorge numbers.