载液粘度对磁场下磁性颗粒链状特征影响的实验与数值分析

Experimental and Numerical Analysis on the Effects of the Carrier Fluid Viscosity on the Chain-like Characteristics of Magnetic Particles Under Magnetic Field

磁性颗粒在许多领域的应用都涉及对其在粘性载液中运动行为的控制。首先采用数字视频显微镜实验测试了磁场作用下不同粘度液体硅橡胶中微米铁颗粒的成链过程;然后基于多磁偶极子理论考虑磁化颗粒的磁场对颗粒磁矩和颗粒间磁力的影响,建立颗粒动力学计算模型,通过与实验结果的对比验证计算模型的正确性;最后结合径向分布函数和颗粒磁势能,采用三维颗粒动力学模型分析载液粘度对颗粒链特征的影响。结果表明颗粒链的形成可分成短颗粒链形成和颗粒链合并联合两阶段。高粘度条件下载液粘性阻力会阻碍短颗粒链联合生长为长颗粒链、“颗粒墙”和粗颗粒簇结构,颗粒链结构达到稳定所需时间增加。随磁场强度的增加载液粘性的影响降低。

The application of the magnetic particles in many fields involves the control of their motion behavior in the viscous carrier fluids.The chain-like structure formation process of the micrometer-scale iron particles in liquid silicone rubber with different viscosity under the magnetic field was firstly tested by digital video microscope.Then,based on the multipolar magnetic interaction theory,the influence of the magnetic field generated by magnetized particles on the magnetic moment of particles and the magnetic interaction forces among particles are calculted,and the particle dynamics model is established.The model is verified by comparing the model prediction with the experimental results.Lastly,based on the calculation and analysis on the radial distribution function and the magnetic potential energy of particles,the three-dimensional particle dynamics model is used to analyze the influence of the carrier fluid viscosity on the chain-like characteristics of magnetic particles.The results show that the formation process of particle chains can be divided into two stages:the formation of short particle chains and the combination and growth of the short particle chains.In the highly viscous carrier fluid,the high fluid resistance will prevent the combination and growth of the short particle chains into long particle chains,"particle walls"and thick chain-like particle clusters.The time required for the magnetic particles to form the final stable chain-like particle structures is increased with the carrier fluid viscosity.The effect of the carrier fluid viscosity is reduced with the applied magnetic field strength.