Behavior of suspended magnetic and nonmagnetic micrometer-size particles in a micro-tube filled with a magnetic fluid is investigated by using the discrete particle method based on the simplified Stokesian dynamics in order to know the polishing process of inner wall of a tube. It is shown that the chain-like clusters of magnetic particles are surrounded by clusters of nonmagnetic particles in the presence of uniform magnetic field. The clusters are held in the field direction in case of rotation of the micro-tube and in case of rotation of magnetic field.

� �Yasushi IDO (Mem.), Kazuya ARAKAWA, Hirotaka SUMIYOSHIBehavior of micrometer-size magnetic particles in a simple shear flow of magnetorheological fluids is investigated by using numerical simulation. Hybrid simulation method which combined both HSMAC method and discrete particle method based on the simplified Stokes dynamics is performed. Behaviors of magnetic particles in shear flows between two parallel plates are simulated. Chain-like clusters appear and they are combined each other to form wall structure in the presence of magnetic field in the static state. In the weak shear flow, such clusters move with flow, however, magnetic particles are rearranged as layered sheet-like structure in the rather strong shear flow.

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