Crown rupture during droplet impact on a dry smooth surface at increased pressure

TL;DR

This study experimentally investigates how increased environmental pressure affects droplet impact dynamics, revealing that higher pressure promotes crown splashing and rupture, and lowers the impact speed threshold for splashing.

Contribution

It provides new experimental insights into droplet impact behavior at high environmental pressures, extending understanding beyond standard pressure conditions.

Findings

High environmental pressure causes crown splashing in a 'thread rupture' mode.

Secondary droplet sizes increase with environmental pressure.

The impact speed threshold for splashing decreases as pressure increases.

Abstract

The impact of droplets at increased environmental pressure is important in many industrial applications. Previous studies mainly considered the impact process at standard or reduced environmental pressure, and the effect of high environmental pressure is unclear. In this study, we experimentally investigate the impact of ethanol droplets on dry smooth surfaces at increased environmental pressure. The effects of the environmental pressure on the splashing and rupture of the crown during the impact process are analyzed. The results show that surrounding gas with high environmental pressure can lead to the splashing of the crown in a 'thread rupture' mode and the sizes of the secondary droplets from the rim of the liquid crown increase with the environmental pressure. The threshold for the transition from spreading to splashing during the impact process is obtained based on the theory of aerodynamics analysis of the lamella. At increased environmental pressure, the threshold speed of the impact decreases with increasing the environmental pressure because the wedge of the lamella is prevented from moving forward and is driven to detach from the substrate by the air ahead, which has a higher density due to the higher environmental pressure.