A numerical computation of the dynamic flow of charged toner particles on a traveling electrostatic wave device is presented. In contrast to simple single particle models, the simulation is performed for a large ensemble of toner particles and takes into account mechanical and electrical interactions. This more realistic computation is based on a two-dimensional finite element field calculation of the imposed traveling electrostatic wave. The particles are modeled as spheres of different sizes, each carrying a point charge inside. Boundary conditions at the substrate surface are met by the method of image charges. Collective electrostatic effects that tend to force the particles towards the conveyor surface are described by an additional electric field accounting for the space charge in the toner cloud. Besides the mutual electrical interactions, collisions between the particles and impact forces at the conveyor surface are included in the calculations as well. Simulations with an ensemble of 250 particles are shown and discussed relative to experimental results.