THE SMALL SHEAR RATE RESPONSE OF ELECTRORHEOLOGICAL SUSPENSIONS .1. SIMULATION IN THE POINT-DIPOLE LIMIT

The electrorheological (ER) response is defined as the rapid and reversible change in the rheological properties of nonaqueous suspensions due to the application of large electric fields [approximately O(1 kV/mm)]. Orders of magnitude increases in suspension viscosities at small shear rates are commonly observed, and are believed to be due to the field-induced formation of fibrous structures. A molecular dynamics-like simulation technique is developed to investigate the ER response at small shear rates. The suspensions are modeled as monodisperse suspensions of hard, dielectric spheres contained in a Newtonian fluid between parallel plate electrodes, and subjected to electrostatic and hydrodynamic forces. The results predict a dynamic yield stress with a concentration dependence that agrees well with experimental results. The magnitudes of the simulated stresses are smaller than the experimental values, a result of approximations in the model. This issue is addressed in the second paper of this series.