日本機械学会論文集 B編
Online ISSN : 1884-8346
Print ISSN : 0387-5016
粒子軸に垂直な磁気モーメントを有する強磁性棒状粒子の単純せん断流中での配向分布と輸送係数に関する研究
佐藤 明尾崎 正孝石川 哲平間島 保
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71 巻 (2005) 708 号 p. 2038-2046

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We have investigated the influences of the magnetic field strength, shear rate, and random forces on transport coefficients such as vicosity and diffusion coefficient and the orientational distributions of rodlike particles of a dilute colloidal dispersion. This dispersion is composed of ferromagnetic spheroidal particles with a magnetic moment normal to the particle axis. In the present analysis, these spheroidal particles are assumed to suffer from the rotational Brownian motion in a simple shear flow and an external magnetic field. The basic equation of the orientational distribution function has been derived from the balance of the torques and solved numerically. The results obtained here are summarized as follows. For a very strong magnetic field, the rodlike particle is significantly restricted in the field direction, so that the particle points to a direction normal to the flow direction (and also to the magnetic field direction). However, the present particle does not exhibit a strong directional characteristic, which is one of typical properties for the previous particle with a magnetic moment parallel to the particle axis. That is, the particle can rotate around the axis of the magnetic moment, although the magnetic moment nearly points to the field direction. The viscosity significantly increases with the field strength, as in the previous particle model. The particle of a larger aspect ratio leads to the larger increase in the viscosity, since such elongated particles induce larger resistance in a flow field. The diffusion coefficient under circumstances of an applied magnetic field is in reasonable agreement between theoretical and experimental results.

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