EFFECTS OF NONUNIFORM ELECTRIC-FIELD ON SLIT FLOW OF AN ELECTRORHEOLOGICAL FLUID

In this work, slit flow of an electrorheological (ER) fluid is studied via laser Doppler anemometry under nonuniform electric-field conditions. For that purpose, the electrodes were coated with a PVC foil. Under ac conditions the ER effect with homogeneous coating was smaller than in the case of no coating. Yet, as soon as holes were punched in the foil, the ER effect greatly increased, exceeding the effect of the uncoated electrodes. Irrespective of the type of coating applied, the electric current remained the same. This contrasts with the results under de conditions where(i) the ER effect with coating (irrespective of the type of coating) was smaller (or even zero) than without coating and where (ii) a decrease of the ER effect always was accompanied by a decrease in electric current. No electric current implied no ER effect, irrespective of the strength of the applied electric field. (C) 1995 Society of Rheology.