Numerical Simulation Of The Two-dimensional Movement Of Magnetic Liquid Droplets Under An External Magnetic Field

Ferrofluid is a colloidal suspension formed by the magnetic nanoparticles uniformly distributed in the carrier liquid.It has both liquid fluid ity and magnetizability of magnetic materials.The application of an external magnetic field can effectively and non-contactly manipulate ferrofluids or droplets,which is considered to be an ideal transport method.The dynamic behavior of ferrofluid droplets in magnetic fields is extremely complex.The coupling mechanis m of magnetic field and flow field is still unclear.In this paper,a preliminary attempt and exploration study on the transport of ferrofluid droplets is made to reveal the influence of external magnetic field on the movement and deformation of ferrofluid droplets,and provide a reference for the further exploration of ferrofluid droplet transport.Based on VOSET interface tracking method,the magnetic force and surface tension are coupled into the momentum equation of the two-phase flow of ferrofluid,and the governing equations of the two-phase flow of ferrofluid are formed with Maxwell’s equations,thus establishing two-dimensional rectangular coordinates.A physical mathematical model of a two-phase flow of ferrofluid in a system.The numerical simulation of the falling process of the droplets in the center of the horizontal tube in a uniform magnetic field is carried out,and the ferrofluid strength,magnetic susceptibility,surface tension,viscous force and the direction and direction of the ferrofluid droplets are discussed in detail.influences.The ferrofluid droplets in the magnetic field are mainly dependent on the magnetic field strength and its own magnetic susceptibility.The jet action produced when the ferrofluid droplets move in the static non-magnetic medium causes the droplets to retract in the direction of motion,and the strength of the jet is related to the dimensionless number Re.The surface tension at the phase interface hinders the deformation of the droplets,and the drop of the ferrofluid droplets in the horizontal tube is significantly affected by the wall effect,and the velocity of the droplets is drastically reduced by the wall effect.A horizontal gradient magnetic field was constructed in the calculation area,and preliminary experiments and exploratory numerical studies were carried out on the transport of droplets on the horizontal tube axis.The gradient magnetic field not only changes the shape of the magnetic liquid droplets,but also provides a driving force for the transport of the ferrofluid droplets,thus demonstrating that a simple gradient transporting ferrofluid droplets is feasible.The ferrofluid droplets that move horizontally in a horizontal gradient magnetic field,the greater the magnetic field strength,magnetic susceptibility and droplet radius,the greater the deformation and velocity of the droplets;in contrast,the greater the viscosity of the surrounding non-magnetic medium The smaller the deformation of the drops.When the magnetic fie ld gradient is small,the surface tension has sufficient time to balance the stretching action of the magnetic force at the head and tail of the droplet,and the droplet appears as a symmetrical flat ellipse;when the magnetic fie ld gradient is large,the magnetic force and the surrounding viscous force are reversed.The droplets are stretched into teardrops under action.