Suspension droplet impact on liquid surfaces

Droplet impact on surfaces is ubiquitous in nature and industrial applications, ranging from raindrop on ocean to spray coating. In many applications, the droplet contains particles which gives rise to new rheological behaviors. Suspension droplet impacting on a solid surface has shown to exhibit interesting behaviors such as jammed states, however, suspension droplet impacting on a liquid surface is less explored. The liquid surface not only provides less resistance to the impact, the capillary interaction between the liquid surface and the droplet combined with the post-impact mixing provide a unique platform to study the jamming and relaxation of the particles in a highly inhomogeneous and transient flow field. In this talk, I will present the suspension droplet impact behaviors on a liquid surface at various impact speeds and suspension volume fractions and discuss the models that predict the behaviors. I will then demonstrate a unique regime where the cavity on the liquid surface is suppressed during the impact and relate it to the jamming relaxation of the particles. Suspension droplet impact on an immiscible pool will be also discussed to highlight the effect of interfacial tension and confinement.