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 conditio ns. For that purpose, the electrodes were coated with a PVC foil. Unde r ac conditions the ER effect with homogeneous coating was smaller tha n 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 un coated electrodes. Irrespective of the type of coating applied, the el ectric current remained the same. This contrasts with the results unde r de conditions where(i) the ER effect with coating (irrespective of t he type of coating) was smaller (or even zero) than without coating an d where (ii) a decrease of the ER effect always was accompanied by a d ecrease in electric current. No electric current implied no ER effect, irrespective of the strength of the applied electric field. (C) 1995 Society of Rheology.