Effect of electrode morphology on the behaviour of electrorheological fluids in torsional flow

In this study, we report experiments on experimental and commercial electrorheological (ER)-fluids in torsional flow. A torsional flow device (clutch) suitable for ER-fluids was designed and constructed. The flow curves measured with this device were compared with flow curves from a conventional rotational viscometer (a concentric-cylinders system). The agreement between the two devices was encouraging. To study the influence of inhomogeneous flow conditions besides the influence of the inhomogeneity of the electric field on the behaviour of an ER-fluid in a clutch mechanism, a set of smooth plates and three further sets of plates with different surface finishes were used in this investigation. Relative to the smooth plates, an increase in the relative ER-effect resulted from both ER-fluids used, when the oblique plates were used in an AC- and DC-field. This improvement in ER-effect seems to be tied to the increase in local field strength at the thick rim of the oblique plate. The addition of metal sheets to the smooth plates of the clutch provided a small increase in ER-effect under AC conditions. But in DC-field, the increase in ER-effect relative to that for smooth plates was rather pronounced, but so was the increase in electric current.