竖直振动颗粒床对流机制的颗粒尺度实验研究

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。

Experimental Study of Particle Size in Convection Mechanism of Vertically Vibrated Particle Bed

In order to get convection movement pattern and formation mechanism formed in a vertically vibrated granular bed, experimental study was carried out by using high-speed photography. It was found that with the increase of vibration acceleration, the particle layers covered by convection loop and the convection intensity significantly increase. By analyzing the evolution of particle velocity vector, the propagation information of various stress waves controlling convection movement in granular bed can be obtained, and the close relation between the stress wave intensity and duration with the vibration acceleration was revealed. Experiments discover that convective movement originated the irreversible transition of particles at the gravity wave front from the side wall to the center of particle bed. This lateral convection intensity is closely related to the curvature of gravity wave front, and its duration changes with the change of vibration cycle of granular bed.