Oblique drop impact onto a deep liquid pool

TL;DR

This study investigates oblique drop impacts on deep liquid pools, identifying impact regimes, quantifying cavity dynamics, and providing scaling laws that incorporate impact angle and Weber number, advancing understanding beyond perpendicular impacts.

Contribution

It introduces a detailed analysis of oblique impacts, including regime classification and scaling laws, which were previously less understood compared to perpendicular impacts.

Findings

Three impact regimes identified: smooth, directional splashing, and omnidirectional splashing.

Cavity axis angle matches impact angle regardless of Weber number.

Cavity depth and displacement depend on Weber number and are modeled using energy considerations.

Abstract

Oblique impact of drops onto a solid or liquid surface is frequently observed in nature. Most studies on drop impact and splashing, however, focus on perpendicular impact. Here, we study oblique impact of 100-micrometer drops onto a deep liquid pool, where we quantify the splashing threshold, maximum cavity dimensions and cavity collapse by high-speed imaging above and below the water surface. Gravity can be neglected in these experiments. Three different impact regimes are identified: smooth deposition onto the pool, splashing in the direction of impact only, and splashing in all directions. We provide scaling arguments that delineate these regimes by accounting for the drop impact angle and Weber number. The angle of the axis of the cavity created below the water surface follows the impact angle of the drop irrespectively of the Weber number, while the cavity depth and its displacement with respect to the impact position do depend on the Weber number. Weber number dependency of both the cavity depth and displacement is modeled using an energy argument.