Predicting the Splash of a Drop Impacting a Thin Liquid Film

Area of Science:

• Fluid Dynamics
• Surface Science
• Experimental Physics

Background:

• Droplet-film interaction is crucial in various industrial processes.
• Understanding splash and deposition phenomena is key to controlling these processes.
• Existing models often lack comprehensive characterization across diverse fluid properties.

Purpose of the Study:

• To experimentally investigate the dynamics of a droplet impacting a thin stagnant liquid film.
• To characterize the transition between liquid deposition and splashing.
• To develop a predictive correlation for the splash/no-splash threshold.

Main Methods:

• Utilized high-speed digital imaging for real-time, high-resolution capture of droplet impact dynamics.
• Employed five distinct liquids to cover a wide range of viscosities and surface tensions.
• Systematically varied drop diameter and impact velocity to explore parameter space.

Main Results:

• Identified key dimensionless parameters governing droplet impact outcomes: Reynolds number (Re), Bond number (Bo), and Morton number (Mo).
• Established a novel correlation, Re = ϕ(Bo, Mo), to predict the splash/no-splash boundary.
• Experimental results showed excellent agreement with the derived correlation and existing literature data.

Conclusions:

• The splash/no-splash threshold is effectively predicted by a correlation involving inertial, viscous, and capillary forces.
• The developed correlation provides a robust tool for anticipating droplet impact behavior.
• This research advances the fundamental understanding of droplet-film interactions across various liquid properties.