Simulation of Brownian Electro- and Magnetorheological Suspensions

Electro- and Magnetorheological (ER/MR) suspensions have various applications in our real world. These ER/MR materials can be used as dampers in artificial knees and robots, as shock absorbers in cars, in power transmission (brakes and clutches), and in fluid control for hydraulic valve. Under the applied electric/magnetic field, dipole-dipole interactions will occur and change the local field environment, resulting in dramatic field-induced change in rheological properties of ER/MR suspensions. However, in some applications of ER/MR suspensions in electric devices, it is sometimes undesirable to have tremendous changes in rheological properties while improving and reinforcing the electrical properties.

To control the strength of the ER/MR effect and study the rheological and electrical properties of the system in interest, we employ a particulate level Brownian Dynamics (BD) simulation to capture the trajectories of dispersed particles in a continuous phase to characterize the suspension properties. This simulation allows us to associate the macroscopic rheological and electrical properties with the microstructure of the suspension and enables us to study the impacts of different simulation parameters, such as particle size, particle volume fraction, shear flow rate, particle shape, the strength of applied fields, etc., on the microstructure and macroscopic materials properties, including the dynamic yield stress, the plastic viscosity, as well as the relative dielectric constants, etc. All results from the BD simulation could provide a guidance for experiments to make the desirable nanoparticle suspensions as we expected.