Kinematic characterization of free-falling near-spherical droplets impacting a viscous liquid film

Abstract

 In industrial settings, the flow characteristics of liquids are pivotal in processes such as piping, mixing, and filtration. A thorough understanding of liquid flow behavior under diverse conditions is essential for optimizing industrial processes and enhancing productivity. This paper investigates a specific fluid dynamic phenomenon: the motion of a liquid droplet interacting with a soap film. The experimental variables include droplet release height, droplet diameter, soap film inclination angle, and soapy water concentration—all of which influence the droplet’s motion characteristics. During the experiments, three distinct phenomena were observed under different conditions: the droplet traversed the soap film, merged into the film, or was repelled by it. A review of the literature reveals that prior studies have primarily focused on these phenomena in isolation, overlooking the combined effects of the aforementioned experimental variables. To address this gap, this thesis proposes a surface tension model for the soap film, systematically analyzes the force balance and energy conversion mechanisms of near-spherical droplets, and derives preliminary relationships between the variables and droplet motion characteristics. Through controlled-variable experiments, the observed phenomena were found to align closely with theoretical predictions, validating the proposed theoretical model’s accuracy.