STEADY AND TRANSIENT RESPONSES OF ELECTRORHEOLOGICAL SUSPENSION PASSING THROUGH A RECTANGULAR CHANNEL

The steady and transient responses of ER effect of ER fluids containin g sulfonated polymer particles, passing through a rectangular channel between two fixed parallel electrodes, were investigated by ensuring p ressure drops across the channel in which the flow established a Poise uille 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 s tress 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 rh eometer decreased suddenly at low shear rate, and reached almost const ant level. That is, the measured yield stress depends on the flow geom etry and the type of applied electric field. The measured pressure res ponse to a step input voltage can be approximated by a first order res ponse, and the rising rime constant of ER effect depend on the composi tions of ER fluids and range from 5 to 40 msec.