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This paper presents a numerical-analytic solution for the flow of a ferrofluid in the annular gap between two concentric cylinders induced by a rotating magnetic field. Unlike analytical solutions presented in the literature, this analysis takes into account the effect of the terms ω x M and V ·M in the magnetization equation which are commonly disregarded in order to decouple the magnetic hydrodynamic problem obtaining in this way an analytical solution. However, it was found that its effect is negligible under the assumption that the magnetization vector of the ferrofluid is proportional to magnetic field vector. The numerical results show a good agreement with the asymptotic solution reported by Chaves et al. 2010. We also review the range of application of this analysis and others reported in the literature made under assumption of proportionality of the vectors of magnetization and magnetic field. [ABSTRACT FROM AUTHOR]

In this work, the obtention of an aqueous ferrofluid is presented. Magnetite particles were prepared by a coprecipitation method, mixing Fe (II) and Fe (III) salts in the presence of sodium polyacrylate and Tween 80. Size of magnetic particles was determined by Laser light scattering. Also the ferrofluid was characterized by Mossbauer Spectroscopy and X-Ray Difraction. These techniques showed that the product sinthetized has a particle size as well as magnetic and chemical characteristics that make it suitable for potential application in biological system. [ABSTRACT FROM AUTHOR]