Constitutive equations for electrorheological fluids based on molecular dynamics

Abstract

Publisher Summary This chapter presents the first physics principle to derive constitute equations for electrorheological (ER) fluids based on molecular dynamics. The computer simulations are applied to investigate the structure of ER fluids. The formation of structure is driven by dipolar interactions, viscous drag forces, and brownian motions. Molecular simulations on this model have shown that the ER fluid can readily form the body-centered tetragonal (bct) lattice under a strong electric field. Several other computer simulations on a similar model are reported. In the extensive simulations, the detail of the induced ER structure under various conditions is examined. The results indicate that ER fluids under an electric field may develop into five different structures under different conditions. In a weak electric field, ER fluids can move from a liquid state to a nematic liquid crystal state, which only has ordering in the field direction, but no ordering in other directions. This ordering indicates chain formation along the field direction. In both liquid and liquid crystal states, the columnar particle density remains uniform. When the electric field is strong and the thermal fluctuation is weak or moderate, ER fluids develop into a bct lattice. The simulation also provides information about the solidification and the chain formation time in ER fluids.