Interface Dynamics of Droplet Impact onto a Viscoelastic Liquid Pool

The impact of droplets on a liquid pool is widely present in various fields such as inkjet printing, spray coating, and oil recovery. While the influence of the droplet phase, such as viscosity and surface tension, on impact dynamics has been extensively investigated, the role of the pool phase, especially in the viscoelastic scenario, remains less understood. In this work, we experimentally and numerically study the impact dynamics of oil droplets on an immiscible liquid pool of polymer aqueous solutions. We find that after droplet impact, the elasticity of the viscoelastic liquid pool could enhance the curvature of the cavity, reduce its depth, and shorten the length of the forward jet, which are further confirmed by direct numerical simulations. Intriguingly, we also find a nonmonotonic dependence of the threshold of Reynolds number for droplet bouncing on the polymer concentration, which can be linked to the critical overlap concentration of the polymer solution. Our findings enrich the understanding of droplet impact onto viscoelastic liquids and may contribute to the development of advanced technologies, for instance, 3D printing and droplet encapsulation.