Classification of Aggregate Structure of Ferrofluids under Condition of Strong Magnetic Fields and Simple Shear Flow Fields

Ferrofluids make aggregations under a strong magnetic field. Therefore, the rheological property becomes complex and nonlinear. In this research, the numerical analysis of the aggregation of ferrofluids under the strong uniform magnetic field and simple shear flow field was made by the Stokesian dynamics method. Results obtained are as follows. (1) The aggregate structure can be classified into four types : the cylindrical structure type, the layered structure type, the diagonal structure type and the corrupt structure type. (2) The apparent shear viscosity by magnetic force shows a characteristic peculiar to each aggregate type. (3) The apparent shear viscosity by magnetic force decreases as the shear rate increases. (4) The apparent shear viscosity by magnetic force increases as the saturation magnetization of magnetic particles increases.