Brownian dynamics simulations on the magnetorheological characteristics of a cubic hematite particle suspension

Abstract

In the present study, we have treated a suspension composed of magnetic cubic particles in a simple shear flow situation in order to investigate the dependence of the magnetorheological properties on the aggregate structures by means of Brownian dynamics simulations. An external magnetic field is applied in the direction normal to the simple shear flow. The main results obtained here are summarized in the following. In a weak applied magnetic field, the cubic particles aggregate to form the closely-packed clusters if the magnetic particle-particle interaction strength is sufficiently large. The closely-packed clusters are transformed into chain-like clusters with increasing magnetic field strength. These chain-like clusters tend to incline in the flow field direction from the magnetic field direction. Since the chain-like clusters give rise to a large resistance to the flow field, the net viscosity of the suspension is increased. As the magnetic field strength is further increased, wall-like structures along the magnetic field direction are formed in the system. In this situation, the force to accelerate the flow field arises due to the characteristic of the particle arrangement within the wall-like clusters, which induces a decrease in the net viscosity. From these results, we conclude that the magnetorheological effect depends on the internal structures of the aggregates formed in the system. Moreover, we suggest that a cubic hematite particle dispersion may have negative magnetorheological characteristics under the certain conditions.

Keywords

• brownian dynamics simulation
• cubic hematite particle
• rheology
• aggregate structure
• regime change