Variation with distance of the attraction force between spheres and estimation of static yield stress of ER fluids

In order to estimate the static yield stress of a suspension of monodispersed spheres subjected to a DC applied field, the knowledge of the interaction force between spherical particles is required. This question of variation of the attraction force between spheres as a function of their distance is investigated on the basis of the conduction model in the particular case of saturation regime of bulk electrical condition of the liquid. The prediction is tested using a scaled-up two-sphere experimental model for the particles interaction. Then a rough estimate of the static yield stress is derived using a linear approximation of the force dependence of the spacing s between spheres.