NUMERICAL INVESTIGATION ON INTERFACIAL PHENOMENA OF FERROFLUID BY LATTICE BOLTZMANN METHOD

ABSTRACT Ferrofluid, also known as magnetic fluid, is a new-type fluid whose property and morphology can be controlled by the external magnetic field. It mainly consists of carrier fluid and suspended magnetic particles (diameter usually 10 nanometers or less). Ferrofluids behave as a smart or functional fluid and has been finding more and more applications in a variety of fields such as electronic packing, mechanical engineering, aerospace, bioengineering, and thermal engineering. It has therefore recently attracted many researchers' interest. Due to the nanosize particles and complex interactions between the nanoparticles and carrier fluid, it is difficult to get insights into ferrofluid by pure experimental or theoretical study. To fully understand the mechanism of ferrofluid, efficient and robust computational methods for the numerical simulation of their dynamical behavior are constantly in high demand. Several numerical models have been proposed for ferrofluid. Over the last decade, lattice Boltzmann method, a new mesoscopic approach, has emerged as a powerful tool for the numerical investigation of a broad class of complex flow, including multicomponent and multiphase flows. Compared with other numerical methods, lattice Boltzmann method, which is based on kinetic theory, has advantages to deal with the interfacial interactions of multiphase flow in micro/nano scale. In the present study, we present a multicomponent lattice Boltzmann model to simulate ferrofluid. In this model, the interactions between internal and external forces of ferrofluid are considered. To validate the coupling of the magnetic field, the velocity field and the evolution of the interface, the steadystate shape of the ferrofluid droplet is analysed. Then the influence of the external magnetic field on the ferrofluid droplet formation and deformation process is numerically investigated. The parameters affecting the interfacial phenomena of ferrofluid, including the magnetic Bond number and the susceptibility, are discussed in this paper. The change in the droplet size and the magnetic strength is simulated. The simulation results show the ferrofluid droplet size increases with increasing magnetic strength. All the results are also compared with previous numerical or experimental studies. The simulation results presented in this paper indicate that lattice Boltzmann method is a capable method to study complex magnetic fluid phenomena. It is also hoped that the simulation results offer helpful information on controlling ferrofluid in our practical applications