Frequency-induced structure variation in electrorheological fluids

We show that by changing the frequency of the externally applied electric field there can be significant variation in the column structure of the electrorheological (ER) fluids, with attendant yield stress implications. This phenomenon is quantitatively explained by the Debye-type relaxation associated with ER fluids' solid particles. First-principle predictions based on the Debye-type dielectric constant are in excellent agreement with the experiments. (C) 2000 American Institute of Physics. .S0003-6951.00.01649-1.