Discrete element study of viscous flow in magnetorheological fluids

Abstract

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

Influence of hydrodynamic drag model on shear stress in the simulation of magnetorheological fluids

“…For the present work, the physically motivated Hertzian repulsion law was chosen instead. A comparison between the Hertzian repulsion law and the traditionally used exponential repulsion showed that both models should be equally suited for the use in MRF simulations [18]. The Hertzian contact force of particle j on particle i is given by…”

Magnetorheology: a review

“…In a subsequent paper by the same authors, an extensive DEM study was performed to elucidate the rupture mechanisms behind the yielding process in MRFs. 180 They identified three different patterns: chains, sheets and columns. For each of the three structure types a corresponding failure mechanism was identified.…”

Study on wall-slip effect of magnetorheological fluid and its influencing factors

“…Unlike the conventional experimental analysis, some scholars used numerical simulation methods to study the mechanism of wall slip. The relationship between the particle structure and wall under different magnetic field intensities was analysed in detail using the discrete element method (Lagger et al, 2014). It was proposed that the magnetic field distribution is the key to the relationship between the particle structure and wall; three different failure mechanisms of the particle structure were reported.…”