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.

垂直振动下的颗粒系统表现出一系列对流模式。仍然缺乏对多种对流模式的普遍和令人信服的解释，这阻碍了颗粒对流的工程应用。本文通过离散元法模拟和设计实验研究了振动流化颗粒系统中多重对流模式的起源。结果表明，参与对流的粒子轨迹呈现出一组随机行走曲线。振动周期中的对流包括碰撞和减速过程。颗粒体系在减速过程中形成纵向位移差，在碰撞过程中完成横向迁移。在初始位移差和粒子振幅之间观察到惊人的线性关系。我们证明了容器的不对称性对对流转换有重大影响。一定时间的振动累积触发并放大了容器的静态不对称表现为动态不对称对流。影响程度依次为斜底、斜振、斜边。