Spin-up flow of ferrofluids : Asymptotic theory and experimental measurements
Spin-up flow of ferrofluids : Asymptotic theory and experimental measurements
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DOI：
10.1063/1.2907221
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发表时间：
2008-05
影响因子：
4.6
通讯作者：
A. Chaves;M. Zahn;C. Rinaldi
中科院分区：
文献类型：
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作者：
A. Chaves;M. Zahn;C. Rinaldi
我们处理的流动的铁磁流体在一个圆柱形容器受到一个均匀的旋转磁场，通常被称为自旋的流动。自1967年首次观察到这一现象以来发表的理论和实验结果的回顾表明，示踪粒子表面观测的实验数据不足以评估整体流动理论。我们提出了直接测量的散装流量，通过使用超声波速度剖面法，和扭矩测量水和煤油为基础的铁磁流体，显示流体corotating与字段在一个刚体一样的方式在整个大部分的散装区域的容器，除了附近的空气-流体界面，在那里它被观察到反向旋转。利用正则微扰方法，我们得到了Zaitsev和Shliomis自旋扩散理论的一个推广。该解对于αK = 3scin 2是严格有效的，其中αK是通过使用外加场幅度计算的朗之万参数，并提供了一种方法。
We treat the flow of ferrofluid in a cylindrical container subjected to a uniform rotating magnetic field, commonly referred to as spin-up flow. A review of theoretical and experimental results published since the phenomenon was first observed in 1967 shows that the experimental data from surface observations of tracer particles are inadequate for the assessment of bulk flow theories. We present direct measurements of the bulk flow by using the ultrasound velocity profile method, and torque measurements for water and kerosene based ferrofluids, showing the fluid corotating with the field in a rigid-body-like fashion throughout most of the bulk region of the container, except near the air-fluid interface, where it was observed to counter-rotate. We obtain an extension of the spin diffusion theory of Zaitsev and Shliomis, using the regular perturbation method. The solution is rigorously valid for αK⪡3∕2, where αK is the Langevin parameter evaluated by using the applied field magnitude, and provides a means ...