Evaluation of a governing equation for the macroscopic dynamics of electrorheological fluids

An analytical equation of motion is proposed to model the dynamics of chang e of electrorheological fluids under the influence of simultaneous shear (g amma) and electrostatic (E) fields of force. This is accomplished with the use of constitutive relations written down by Mason and collaborators [A. O kagawa, R. G. Cox, and S. G. Mason, J. Colloid Interface Sci. 47, 536 (1974 )] for the electrostatic and hydrodynamic stresses developed in the fluid. The properties of the suspension are considered in a way that both the diel ectric and conductive characters of particles and suspending fluid are comp rised. From the model results an equation relating eta to E and gamma, a ch aracteristic apparent viscosity, that is not restricted to a simple quadrat ic dependence with E, a usual degree of functional dependence from which mo re recent experimental results, thus far inexplicably, seem to deviate. Exp erimental results will be compared to the theoretical predictions. (C) 2001 American Institute of Physics.