Zamankhan P, Tynjälä T, Polashenski W, Zamankhan P, Sarkomaa P
Department of Energy Technology, Lappeenranta University of Technology, Fin-53851, Lappeenranta, Finland.
Phys Rev E Stat Phys Plasmas Fluids Relat Interdiscip Topics. 1999 Dec;60(6 Pt B):7149-56. doi: 10.1103/physreve.60.7149.
At high solid concentrations, computer simulations of sheared granular materials comprised of randomly arranged, monodisperse, smooth, inelastic spherical particles flowing in a Couette geometry show large fluctuations in the normal stress at the walls. These fluctuations are characterized by a marked asymmetric amplitude distribution similar to those observed in recent experiments. In these systems the particles' mean square displacement in the shear direction is observed to vanish locally which indicates the formation of crystallized regions. However, there are other regions in the system with nonzero values for the mean square displacement in the shear direction. This observation indicates that a sheared monodisperse granular material initially in a disordered state could evolve to a system in which the crystal phase is formed largely with a well-defined interface between different phases. The periodic phase transition is observed between the compressed, highly ordered crystalline state and the dilated, less ordered state of the layer of particles adjacent to the wall, which may explain the stick-slip behavior which occurred in the experiments.
在高固体浓度下，对由随机排列、单分散、光滑、非弹性球形颗粒组成、在库埃特几何形状中流动的剪切颗粒材料进行计算机模拟，结果显示壁面处的法向应力存在大幅波动。这些波动的特征是具有明显的不对称振幅分布，类似于最近实验中观察到的情况。在这些系统中，观察到颗粒在剪切方向上的均方位移在局部消失，这表明形成了结晶区域。然而，系统中其他区域在剪切方向上的均方位移值不为零。这一观察结果表明，最初处于无序状态的剪切单分散颗粒材料可能演变成一个系统，其中晶相在很大程度上形成，不同相之间有明确的界面。在与壁相邻的颗粒层的压缩、高度有序的结晶态和膨胀、无序程度较低的状态之间观察到周期性相变，这可能解释了实验中出现的粘滑行为。
