Torroidal convection roll in a three-dimensional granular system

We study the behavior of a system of inelastic hard spheres in a gravitational field and contained in a cylinder by means of a molecular dynamics simulation with an event-driven algorithm. If energy is supplied to the system by a vibrating bottom wall, the system becomes fluidized and a convection roll, as evidenced by the time-averaged velocity field, appears. The convection is strongly influenced by the value of the particle–side-wall restitution coefficient: for elastic particle–side-wall collisions, the sense of the convection is reversed and the convection intensity is significantly reduced compared with the case of elastic collisions.