Abstract
The temporal evolution of three-dimensional structure in an electroheological (ER) fluid is examined by a computer simulation. A parameter B characterizing the ratio of the Brownian force to the dipolar force is introduced. For a wide range of B, the ER fluid has a rapid chain formation followed by aggregation of chains into thick columns which has a body-centered tetragonal lattice structure. The Peierls-Landau instability of single chains helps formation of thick columns. If the Brownian force is very small, the ER system may be trapped in some local energy-minimum state.