Spreading of viscoplastic droplets

TL;DR

This paper investigates how viscoplastic droplets spread on thin films, deriving scaling laws, performing asymptotic analysis, and validating findings through simulations and experiments with yield-stress fluids.

Contribution

It introduces new scaling laws and asymptotic analysis for the final shape of viscoplastic droplets, supported by numerical simulations and experimental validation.

Findings

Final droplet shape depends on yield stress and surface tension

Scaling laws accurately predict the final radius of droplets

Numerical and experimental results agree with theoretical predictions

Abstract

The spreading under surface tension and gravity of a droplet of yield-stress fluid over a thin film of the same material is studied. The droplet converges to a final equilibrium shape once the driving stresses inside the droplet fall below the yield stress. Scaling laws are presented for the final radius and complemented with an asymptotic analysis for shallow droplets. Moreover, numerical simulations using the volume-of-fluid method and a regularized constitutive law, and experiments with an aqueous solution of Carbopol are presented.