On Liquid Viscosity Effects on Droplet Splash and Receding Breakup on a Smooth Solid Surface at Atmospheric Pressure

TL;DR

This study investigates how liquid viscosity influences droplet splash and breakup on smooth surfaces, revealing a non-monotonic threshold behavior and proposing a new correlation for predicting splashing.

Contribution

It introduces a semi-empirical correlation for droplet splash thresholds that accounts for viscosity effects, improving upon previous models.

Findings

Critical Weber number varies non-monotonically with viscosity.

Splash occurs at low viscosity, receding breakup at high viscosity.

New correlation fits experimental data better than existing models.

Abstract

Experimental and modelling study is presented for the effect of a wide range of liquid viscosities on the droplet impact on a smooth solid surface at atmospheric pressure. A non-monotonic variation of threshold between droplet deposition and splash was observed experimentally. Specifically, the critical Weber number separating deposition from splashing decreases and then increases with increasing the Ohnesorge number. The observations of splash in low viscosity region and receding breakup in high viscosity region were analyzed qualitatively from the perspectives of Kelvin-Helmholtz instability and Rayleigh-Taylor instability, respectively. Based on instability analysis for the viscosityinduced nonmonotonicity, a new semi-empirical correlation of droplet splashing thresholds is proposed by fitting experimental results from previous and present data and shows better performance than previous correlation formulas.