Abstract Dye-tracing and concentration-measuring experiments are carried out to investigate the magnetophoresis of magnetic nanoparticles (MNP) in the presence of an external cylindrical permanent magnet. The magnetophoresis of MNP, inducing an obvious forced-convective flowing of the carrier fluid, which can be observed by visualizing flowing of carrier fluid, results in a temporal and spatial variation of particle concentration. Moreover, in order to get insight into the physical mechanisms of magnetophoresis of MNP, a coupled particle-fluid analysis, in which the non-linear drift-diffusion differential equation is incorporated into the Navier-Stokes equation, is adopted to discuss the influence of particle-fluid interaction on the variation of particle concentration and the kinetics of carrier fluid. It is worth noting that the equivalent current source (ECS) method is adopted to obtain a closed-form field analysis, which provides exactly prediction of the Kelvin force and enables magnetophoretic analysis more efficient. In dye-tracing experiments, an obvious vortex can be observed as the methylene blue moves with the convection of carrier fluid. Furthermore, this phenomenon is also predicted by using the coupled particle-fluid model. A comparison between the experimental and numerical results shows that the hydrodynamic interactions between MNP and carrier fluid plays an important role in inducing forced-convective flowing of carrier fluid and enhancing the magnetophoresis of MNP. Furthermore, these results also denote that the coupled particle-fluid model provides a more efficient and accurate method in investigating the magnetophoresis of MNP.

中文翻译：

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圆柱形永磁体作用下磁性纳米粒子的磁泳实验与数值分析

摘要 进行染料示踪和浓度测量实验以研究在外部圆柱形永磁体存在下磁性纳米粒子 (MNP) 的磁泳。MNP 的磁泳引起载液明显的强制对流流动，这可以通过可视化载液的流动来观察，导致粒子浓度的时空变化。此外，为了深入了解MNP磁泳的物理机制，采用耦合粒子-流体分析，其中将非线性漂移-扩散微分方程纳入纳维-斯托克斯方程，讨论了MNP的影响颗粒-流体相互作用对颗粒浓度变化和载液动力学的影响。值得注意的是，采用等效电流源（ECS）方法获得封闭形式的场分析，可以准确预测开尔文力，使磁泳分析更有效。在染料示踪实验中，当亚甲蓝随着载液的对流移动时，可以观察到明显的涡流。此外，这种现象也可以通过使用耦合粒子-流体模型来预测。实验和数值结果的比较表明，MNP 与载液之间的流体动力学相互作用在诱导载液强制对流流动和增强 MNP 的磁泳方面起着重要作用。此外，