Abstract
Hydrous electrorheological (ER) fluid was poured into the annular interstitial space between two coaxial cylinders : the outer cylinder can rotate on its axis and the inner stationary one is connected to a torque meter. Upon application of an electric field and rotation of the outer cylinder, measurements of velocity distributions of ER fluid in the annular space were made using a laser Doppler velocimeter and those of shear stress exerted on the inner cylinder surface were made using the torque meter. When the rotational speed was very low, the flow was observed directly. Since high-water-content ER fluid requires a high electric current, a countermeasure for reducing the current was also examined. It was found that the ratio of electrical force to viscous force (= the inverse of the Mason number) plays an important role in determining the flow pattern of ER fluid and, upon increasing the magnitude of the ratio, the flow pattern varies from Couette flow to plug flow. Insulation of the inner cylinder surface with thin polyethylene films and a rubber membrane reduced the electric current but the magnitude of the generated shear stress decreased to one-tenth of that without insulation films.
