Impacts on viscous fluids: on ejecta, corolla and splashes

TL;DR

This study combines experiments and simulations to analyze how liquid viscosity and air pressure influence the formation of ejecta, corolla, and splashes during drop impacts on viscous liquid pools, revealing two distinct spreading sheets.

Contribution

It introduces a detailed analysis of the impact dynamics on viscous pools, highlighting the roles of two separate sheets and the effects of viscosity ratios, which was not previously well understood.

Findings

Two distinct sheets form during impact: ejecta and substrate-fed.

Viscosity ratio significantly affects splashing behavior.

Impact dynamics vary with liquid viscosity and air pressure.

Abstract

We investigate both experimentally and numerically the impact of liquid drops on deep pools of aqueous glycerol solutions with variable pool viscosity and air pressure. With this approach we are able to address drop impacts on substrates that continuously transition from low-viscosity liquids to almost solids. We show that the generic corolla spreading out from the impact point consists of two distinct sheets, namely an ejecta sheet fed by the drop liquid and a second sheet fed by the substrate liquid, which evolve on separated timescales. These two sheets contribute to a varying extent to the corolla overall dynamics and splashing, depending in particular on the viscosity ratio between the two liquids.