CFD simulation of equilibrium shape and coalescence of ferrofluid droplets subjected to uniform magnetic field

In this study a computational framework has been presented to simulate the equilibrium shape and coalescence behavior of suspended ferrofluid droplets subjected to uniform magnetic field. A finite volume based CFD Open source solver library (OpenFOAM (R)) is used for the simulations. Coupled flow field equations and magnetostatic equations are numerically solved and a coupled scheme of Volume of Fluid (VOF) and Level-Set (LS) methods called S-CLSVOF is implemented for interface capturing. The simulation results are compared with the experimental data reported in the literature. The effects of different parameters, such as magnetic field intensity, magnetic susceptibility, surface tension and initial size of droplet on the deformation of magnetic droplet are investigated. Aspect ratio of droplet at the equilibrium state is calculated and a cubic polynomial is proposed to formulate its dependency to the magnetic Bond number and magnetic susceptibility. Finally the coalescence of two falling ferrofluid droplets under the effect of uniform magnetic field is simulated. The results reveal that the application of magnetic field has a significant effect on the coalescence of droplets and it can be used as a promising method for emulsion breaking. (C) 2015 Elsevier B.V. All rights reserved.