Interparticle forces in electrorheological fluids: effects of polydispersity and shape

We describe a numerical approach to compute the dielectrophoretically induced forces between particles for a polydisperse electrorheological (ER) fluid. The method is based on the solution of an integral equation for the charge density on the dielectric interfaces between particles and medium. It is used for calculating forces between particles of arbitrary size and shape (only restricted to axial symmetry). Results for the interaction between spheres, spheroids, rods and circular cylinders of different sizes are discussed. The analysis shows the strong influence of multipolar interactions at short distances and high dielectric contrast, as well as the importance of using accurate modelling of particle shape.