MACROSCOPIC MODEL OF INTERACTION BETWEEN PARTICLES IN AN ELECTRORHEOLOGICAL FLUID

The particle-particle interaction in an electrorheological fluid is investigated starting from the basic remark that, under DC conditions, the electric field distribution is controlled by the conduction properties of both solid particles and carrying liquid. An experiment on a large scale model sphere of very slightly conducting material facing a metallic plate is developed in particular by varying the even weaker but controlled conductivity of the surrounding liquid. The measurement of the attraction force between sphere and plate reveals two regimes of variation of the force as a function of the applied electric field. An approximate analysis taking into account the non-linear character of electrical conduction of the liquid at high electric fields leads to formula which fairly well account for the observed dependence on the electric field as well as on the ratio GAMMA of solid and liquid conductivities.