A non-uniform magnetic field coupled lattice Boltzmann model and its application on the wetting dynamics of a ferrofluid droplet under gravity effects

Abstract

To extend the mesoscopic model for simulating the wetting dynamics of ferrofluid droplets, an improved multicomponent multiphase pseudopotential lattice Boltzmann (LB) model coupled with the magnetic field solver is constructed in this work. Through a series of validation studies, the accuracy and reliability of the proposed coupled model are ensured. The ferrofluid droplet is subjected to the effects of non-uniform magnetic field and gravity. The influences of various magnetic Bond numbers (Bom) and gravitational Bond numbers (Bo) on the wetting dynamics of a ferrofluid droplet on a hydrophobic surface are discussed, and the mechanism behind the morphological evolution of the ferrofluid droplet is unveiled. The results show that the curvature of the phase interface is a key factor influencing both the magnetic field intensity distribution around the phase interface and the pressure distribution inside the ferrofluid droplet, thus changing the evolution of the droplet morphology. The variation of Bom has a monotonic impact on the morphological evolution of the ferrofluid droplet and its equilibrium state, while the effect of the Bo depends on the magnitude of Bom. At Bom=49.98 and Bo=4.1, the ferrofluid droplet splits from the central position and into three parts in the end. The amplitude and duration time of the oscillation of the ferrofluid droplet increase with Bom. This study can provide a model reference and some key theoretical understandings for the numerical study of the wetting dynamics of ferrofluid droplets.