Experimental and CFD Modeling of Sodium Alginate Droplets Impacting Onto Immiscible Deep Liquid Surface

Droplet impingement onto an immiscible but reactant surface is of high study interest because of its wide use in microfluidics and biological cell culture. This work explored the process of a sodium alginate droplet falling, impinging, and settling into an immiscible but reactant CaCl₂ solution experimentally and numerically. In the experimental study, three discernable shapes of droplets are identified, (i) spherical ball (ii) spherical ball with a tail and (iii) a toroidal shape. The shape deformation, contact time, and deformation diameter are governed by We and Oh number, and according correlation are discussed. CFD modeling and simulations are performed to understand the mechanism of the physical phenomenon taking place at the interface, and the bulk phase deformation during and after the droplet impact. The detailed pressure field, velocity field, force analysis, turbulent kinetic energy during the drop impingement process are studied and analyzed comparing with the experimental results. This study can help control the alginate droplet shape by adjusting the initial droplet and solution operational conditions, thus enabling versatile droplet application in fields of biology, food, material and many others.