Computer simulations of ER fluids in DID model

Theoretical investigations on electrorheological (ER) fluids are usually concentrated on monodisperse systems. Real ER fluids must be polydisperse in nature, i.e., the suspended particles can have various sizes and/or different dielectric constants. An initial approach for these studies would be the point-dipole (PD) approximation, which is known to err considerably when the particles approach and finally touch due to multipolar interactions. A dipole-induced-dipole (DID) model is shown to be both more accurate than the PD model and easy to use. The DID model is applied to simulate the athermal aggregation of particles in ER fluids and the aggregation time is found to deviate significantly as compared to the PD model. Moreover, the inclusion of DID force further complicates the results because the symmetry between positive and negative contrasts will be broken by the presence of dipole-induced interactions.