Fundamental study of electrorheological fluids (similarity of velocity profiles)

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