The small shear rate response of electrorheological suspensions. I. Simulation in the pointndash;dipole limit

摘要

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 lsqb;sim;O(1 kV/mm)rsqb;. Orders of magnitude increases in suspension viscosities at small shear rates are commonly observed, and are believed to be due to the fieldhyphen;induced formation of fibrous structures. A molecular dynamicshyphen;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.