Magnetic fluid is a stable suspension of solid phase magnetic particles of diameter about 10 nm in a nonmagnetic carrier fluid like water or alcohol. Nowadays, the magnetic fluid is widely used in industry areas such as sealing, damping, lubricating, sound regulation, heat dissipation, and MHD beneficiation. Researchers have paid great attention to the behaviors of non-magnetic particles (NPs) in the magnetic field because magnetic fluid containing NPs can form different microstructures, which are easily controlled by applying a magnetic field. In order to appropriately use the properties of magnetic fluid in industry, it is necessary to study the interaction among NPs in detail. In this paper, a multi-physical numerical model is employed to investigate the sedimentation of two NPs in magnetic fluid subjected to an applied magnetic field. The magnetic fluid flow is simulated by lattice Boltzmann method, and magneto hydrodynamics is calculated with a self-correcting procedure of a Poisson equation solver, which enables the Ohm's law to satisfy its conservation law. A dipole force model is used to obtain the dipole interaction force between particles. In addition, as the permeability of the magnetic fluid is quite different from those of the NPs and magnetic fluid, correctly establishing the conjugate boundary condition of the magnetic intensity at the interface between the particles and surrounding fluid is a key because it affects the magnetic induction in the fluid-structure interaction area. A smooth transition scheme of the conjugate boundary condition for magnetic intensity at the interface between the particles and surrounding fluid is used in this work. The aim of this work is to investigate sedimentation of two NPs in magnetized magnetic fluid. By changing the ratio of magnetic permeability and the magnetic parameter, it is found that altering the ratio of magnetic permeability is more effective to change the trajectories of NPs, while changing the magnetic parameter can just give rise to a slight transform of particle trajectories. This can provide good theoretical support for the application of magnetic fluid in industry area, because the results in the present simulation can quantitatively analyze the controlling of the movement of NPs.%在磁场作用下,在磁流体里添加非磁性颗粒(non-magnetic particles,NPs),可以使得NPs形成不同的结构,操控NPs的运动从而影响磁流体的特性,这种应用逐渐受到了研究者的关注.为了更好地操控磁流体里NPs的运动,本文采用一种多物理模型研究在外加磁场作用下,磁流体中两个NPs沉降的运动过程.其中,用格子玻尔兹曼方法模拟磁流体的运动,外加磁场对磁流体的影响用一种自修正方法求解泊松方程,这个自修正方法可以使欧姆定律满足守恒定律.NPs之间的偶极干扰力采用偶极力模型,同时采用一种相对过渡平滑的共轭边界条件处理NPs与磁流体交界面的流固干扰以避免磁场密度过渡的突变.本文主要探究两个NPs在磁流体中的沉降,揭示磁场作用下NPs的相互干扰原理;同时,对控制NPs运动时的参数进行调节,得到NPs不同的运动轨迹,达到操控颗粒运动的目的.本研究可对NPs在磁流体中的应用提供定量的分析结果,对NPs在工业上的应用提供有力的理论支撑.
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