Droplet impact onto moving liquids

Abstract

From rain drops landing on the ocean to inkjet printing, the impact of droplets onto moving liquid surfaces is a ubiquitous process in nature and in industry. A rich range of phenomena can arise. The behaviour depends on the inertia, the properties of the drops and the relative speeds in the impact zone. While the result ranges from tranquil coalescence to violent splashing, intermediate regimes also occur, including partial and complete bouncing and even ‘surfing’ of the droplet. These regimes are determined by the ratio of the drop and surface velocities and the liquid properties. A regime diagram can be constructed in which distinct dynamical regimes are clearly identified.

Surfing of drops on moving liquid–liquid interfaces

“…Whether the drops can levitate on the surface or not depends a lot on the impact conditions. A phase map was plotted by Castrejón-Pita et al (2016) to indicate the different patterns using WeRe 1/2 and v t /(v n Re 1/2 ) as coordinates, where v t and v n are the velocity of the surface and the impact velocity of the drop. Drop levitation was observed on the liquid surface at large values of v t /(v n Re 1/2 ), which requires a high viscosity of the liquids, a low impact velocity and a large rotation speed.…”

“…In many industrial applications where the drop is levitated over an interface, including oil petroleum transportation and oil-water separation (Rommel et al 1993), the drops are surrounded by another liquid and the fluid interface is significantly deformed when the drop approaches it because of gravity. In most of the previous investigations, drops were generated in air and approached the interfaces of liquid films with air (Lhuissier et al 2013;Castrejón-Pita et al 2016;Sawaguchi et al 2019). In such cases, drop levitation can be realized only when the interface have high speed and the liquids have large viscosity.…”

Droplet Impact on a Moving Thin Film with Pseudopotential Lattice Boltzmann Method

“…Later, the researchers made different experimental studies on the droplet impact on a moving liquid film. Castrejón-Pita et al [8] studied the process of a droplet impact on the moving liquid film, and four different regimes are obtained, including the tranquil coalescence, violent splashing, partial and complete bouncing, and surfing. e results indicated the splash regimes are determined by the ratio of the velocity of the droplet and liquid film.…”

Hydrodynamically Guided Hierarchical Self‐Assembly of Peptide–Protein Bioinks

“…known to be ruled by liquid properties and force of impact. [40] For example, the forces associated with the impact of the droplet, causes the printed gels to exhibit a larger diameter compared to the original droplet. In our experiments, the toroidal gels were on average ~1.6 times bigger than the initial droplet ( Figure 4d).…”