ELECTROVISCOUS EFFECT IN NONPOLAR LIQUIDS

The apparent viscosity of weakly conducting non-polar liquids flowing between two plates has been found to increase when an electric field (steady and alternative) is applied perpendiculary to the flow direction. The increase in apparent viscosity under both D.C. and A.C. stresses appears in a limited range of conductivity, where the non-dimensional number relating the charge density and the applied voltage multiplied with Onsager's factor (F(b))1/2, C0·(F(b))1/2=(q0·d2)/(ε·ε0·Φ)·(1+(1/2)b+(1/24)b2+·) takes a value of between 0.1 and 10. This phenomenon together with the related appearance of space-charge boundary layers near the electrodes can be explained in terms of an electrohydrodynamic effect. © 1979 IOP Publishing Ltd.