Binary interaction force on spheres I: Low Reynolds number flow

A two-particle distribution function is derived to calculate the effect of the presence of the particles surrounding a test particle. The average drag force exerted on a particle accounting for binary particle-particle intera ctions is calculated assuming low particle-Reynolds number flow. The introd uction of particle-particle interactions results in the prediction of force s that depend on particle concentration and concentration gradients, size g radients and second derivatives of the particle velocity field. Delta and P oisson size distributions were studied explicitly and some predictions comp ared with available experimental data, showing good agreement.