Origin of multiple convection patterns in vibrofluidized granular system

Abstract

Granular system under vertical vibration exhibits a range of convection patterns. A universal and convincing explanation of multiple convection patterns is still lacking, which hinders the engineering application of granular convection. This paper investigates the origin of multiple convection patterns in vibrofluidized granular system through discrete element method simulations and designed experiments. Results reveal that the trajectories of the particles involved in convection exhibit a set of random walking curves. Convection in a vibration period consists of collision and deceleration processes. The granular system forms longitudinal displacement differences in the deceleration process, and completes the lateral migration in the collision process. Striking linear relationships are observed between the initial displacement difference and amplitude of particles. We proved that the asymmetries of the container have a significant impact on the transformation of convection. The accumulation of vibration for a certain time triggers and amplifies the manifestation of static asymmetries of the container as dynamic asymmetric convection. The degree of influence is in the order of inclined bottom, inclined vibration and inclined side.