The steady and transient responses of ER effect of ER fluids containing sulfonated polymer particles, passing through a rectangular channel between two fixed parallel electrodes, were investigated by ensuring pressure drops across the channel in which the flow established a Poiseuille flow geometry. Effects of the types and the strength of applied electric field and the mean flow velocity on the steady response were clarified, and compared with those in a Couette flow geometry using a rotary rheometer in order to investigate the dependence of ER effects on the flow geometry. As the mean flow velocity increased, the yield stress decreased exponentially under DC voltage, while, in the case of AC voltage, gradually increased and reached a peak level and decreased thereafter. Contrastively, the yield stress measured by the rotary rheometer decreased suddenly at low shear rate, and reached almost constant level. That is, the measured yield stress depends on the flow geometry and the type of applied electric field. The measured pressure response to a step input voltage can be approximated by a first order response, and the rising time constant of ER effect depend on the compositions of ER fluids and range from 5 to 40 msec.
ASJC Scopus subject areas
- Statistical and Nonlinear Physics
- Condensed Matter Physics