EFFECTIVE VISCOSITY OF AN ELECTRORHEOLOGICAL FLUID

The viscosity of an electrorheological fluid in an electric field is s tudied by computer simulations. The fluid viscosity increases with the field through three stages. In a weak field, the fluid remains Newton ian although its viscosity increases. At this stage, while drifting in the flow direction, particles diffuse in the direction perpendicular to the flow. In an intermediate electric field, the fluid has tilted a nd broken chains moving with the flow and the fluid becomes non-Newton ian. The viscosity eta and the shear rate gamma has the following rela tionship eta = eta(0) epsilon(-gamma tau) where tau is the relaxation time and eta(0) is exponentially proportional to the dipolar interacti on energy and the volume fraction. In a strong electric field, the flu id contains condensed chains which provide yield stress and hysteresis .