Numerical Study on the Ferrofluid Droplet Splitting in a T-junction with Branches of Unequal Widths using Asymmetric Magnetic Field

Abstract

Research on the microdroplet splitting phenomenon has intensified in recent years. Microdroplet splitting has numerous applications in chemical synthesis, biology, and separation processes. The current paper covers the numerical study of ferrofluid microdroplet splitting at various lengths and velocities inside the T-junction with branches of unequal widths under asymmetric magnetic fields. Microdroplet splitting can be controlled by using an asymmetric magnetic field and the asymmetry in the width of T-junctions branches. Three geometrical models of the T-junction with different widths ratio (0.7, 0.85, and 1), along with a magnetic field with various intensities are studied. This magnetic field is generated by a line dipole. In this study, the distance between the dipole and origin is kept constant. The splitting ratio of ferrofluid microdroplets at different velocities (different capillary numbers), different non-dimensional lengths and different magnetic force (different magnetic Bond numbers) at the center of T-junction are calculated for each amount of branch width. The results are verified with previous works and their correctness is proved. The splitting ratio is defined as the volumetric ratio of the larger daughter droplet to the mother droplet. The results indicate that generally, the stronger the asymmetric magnetic force is, the more asymmetric the splitting will become, with the splitting ratio becoming closer to 1. Also, as asymmetry increases between the widths of the two branches of the T-junction, the splitting ratio approaches 1.