Discrete element study of viscous flow in magnetorheological fluids

Using discrete element simulations, we gain insight into the structure of a magnetorheological fluid (MRF) under shear. In simulations with flat walls, the particles arrange in chains, sheet-like structures, or columns along the magnetic field lines, depending on the strength of the applied external magnetic field. Corresponding to the structure formation, three different types of failure mechanisms can be identified. For the characterization of the different regimes, specific particle coordination numbers are introduced. The three structural regimes can be distinguished and described by means of these coordination numbers. To analyze the contact between the MRF particles and the walls of the shear cell, additional simulations with rough walls have been conducted. The resulting structure formation could be successfully classified by the introduced coordination numbers. Based on the analysis of the shear stress transmission both in the case of flat and rough walls, possibilities for shear stress enhancement for technological applications are discussed.