Creation of prompt and thin-sheet splashing by varying surface roughness or increasing air pressure

TL;DR

This study investigates how surface roughness and air pressure affect liquid splash mechanisms during drop impacts, revealing that roughness promotes prompt splashing but inhibits thin-sheet formation, while lower air pressure suppresses all splash types.

Contribution

It demonstrates the distinct roles of surface roughness and air pressure in controlling splash mechanisms during liquid impacts, providing new insights into splash suppression strategies.

Findings

Roughness increases prompt splashing at the contact line.

Roughness inhibits thin-sheet formation.

Lowering air pressure suppresses both splash types.

Abstract

A liquid drop impacting a solid surface may splash by emitting a thin liquid sheet that subsequently breaks apart or by promptly ejecting droplets from the advancing liquid-solid contact line. Using high-speed imaging, we show that air pressure and surface roughness influence both splash mechanisms. Roughness increases prompt splashing at the advancing contact line but inhibits the formation of the thin sheet. If the air pressure is lowered, droplet ejection is suppressed not only during thin-sheet formation but for prompt splashing as well. The threshold pressure depends on impact velocity, liquid viscosity and surface roughness.