Drop Impact Dynamics: Impact Force and Stress Distributions

Abstract

Dynamic variables of drop impact such as force, drag, pressure, and stress distributions are key to understanding a wide range of natural and industrial processes. While the study of drop impact kinematics has been in constant progress for decades thanks to high-speed photography and computational fluid dynamics, research on drop impact dynamics has only peaked in the last 10 years. Here, we review how recent coordinated efforts of experiments, simulations, and theories have led to new insights on drop impact dynamics. Particularly, we consider the temporal evolution of the impact force in the early- and late-impact regimes, as well as spatiotemporal features of the pressure and shear-stress distributions on solid surfaces. We also discuss other factors, including the presence of water layers, air cushioning, and nonspherical drop geometry, and briefly review granular impact cratering by liquid drops as an example demonstrating the distinct consequences of the stress distributions of drop impact. Expected final online publication date for the Annual Review of Fluid Mechanics, Volume 54 is January 2022. Please see http://www.annualreviews.org/page/journal/pubdates for revised estimates.

Droplet Bouncing: Fundamentals, Regulations, and Applications

“…Possible outcomes of droplet impact are bordered by four contrasting phases which are splashing, spreading, bouncing, and depositing. [1][2][3][4] Among them, droplet bouncing attracts unparalleled research interests owing to its unique features such as minimized contact time (around tens of milliseconds) and negligible energy dissipation (droplet springs by retrieving its kinetic energy). Those features bring about limited heat transfer and rapid liquid removal and benefit various anticipated applications.…”

Droplet Impact on Asymmetric Hydrophobic Microstructures

“… 18 − 22 Theoretical, 23 − 26 numerical, 25 − 28 and experimental investigations 20 , 29 − 35 of droplet impact have also highlighted the fingering of spreading front and the scaling laws for maximum deformation. 2 , 36 , 37 Specific features of droplet rebound such as symmetry break of droplet impact on a curved surface 38 and on macrotextures 39 have also received attention.…”

Stress distribution and surface shock wave of drop impact

“… 16 , 17 and references therein). Very few experiments have been performed probing the dynamic properties of drop impact that are directly responsible for drop-impact erosion 18 . As an important dynamic factor, the impact force of liquid drops has begun to attract attention in recent years 18 – 26 .…”

“…Very few experiments have been performed probing the dynamic properties of drop impact that are directly responsible for drop-impact erosion 18 . As an important dynamic factor, the impact force of liquid drops has begun to attract attention in recent years 18 – 26 . However, it becomes clear from these recent studies that the unusual ability of an impacting drop in erosion cannot stem from its impact force alone, as the maximum impact force induced by a millimetric water drop falling near its terminal velocity is very weak, more than an order of magnitude smaller than that generated by the impact of a solid sphere of similar size, density, and velocity 23 .…”