Experiment study of droplet impacting on a static hemispherical liquid film

Abstract

Experiment study of a droplet impacting on a static hemispherical liquid film was conducted. The static hemispherical liquid film was formed by a first droplet impacting on a dry solid surface, and the diameter, impact velocity, and liquid properties of the second droplet were the same with the first one. A high-speed camera was used to capture the deformation process of the impacting droplet at a shooting speed of 4000 frames per second. The effects of droplet Weber number and Reynolds number on the spread factor and flatness factor were analyzed quantitatively. The result shows that as increasing of droplet Weber number, the phenomena of spread, formation of liquid crown, and splashing occurred subsequently after the droplet impacted on the liquid film. The maximum spread factor of the liquid film after droplet impacting on the static hemispherical liquid film is higher comparing to the case of droplet impacting on the dry solid surface under the same impacting condition. Further, with the increase of droplet Weber number, the maximum spread factor of the liquid film increases. With the decrease of droplet Reynolds number, the maximum spread factor of the liquid film d ecreases and formation of the liquid crown is inhabited.