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为了得到竖直振动颗粒床形成对流的运动模式及形成机制,本文通过高速摄影技术对竖直振动颗粒床进行了实验研究。实验发现,随着振动加速度的增加,对流环覆盖的粒子层数和强度明显增加。通过分析颗粒速度矢量图的演化,可以获得控制对流运动的各种应力波在在粒子床中传播的信息,发现应力波的强度和持续时间与振动加速度密切相关。通过实验发现,对流运动发端于重力波面上粒子从侧壁向粒子床中心的不可逆跃迁,这种横向对流的强度与重力波面的曲率密切相关,而持续的时间随粒子床振动周期的变化而变化。
In order to obtain the motion mode and formation mechanism of convective particle bed formation vertical vibration, this paper carried out an experimental study on the vertical vibrating particle bed by high-speed photography. Experimental results show that with the increase of vibration acceleration, the number and strength of particles covered by convection ring obviously increase. By analyzing the evolution of the particle velocity vector, we can obtain the information about convective motion of various stress waves propagating in the particle bed. It is found that the strength and duration of the stress wave are closely related to the vibration acceleration. The experiment shows that the convection movement starts from the irreversible transition of the particles from the sidewall to the center of the particle bed on the gravity wave surface. The intensity of this transverse convection is closely related to the curvature of the gravity wave surface, and the duration varies with the vibration period of the particle bed .