Dynamics of sheared ellipses and circular disks: effects of particle shape.
Dynamics of sheared ellipses and circular disks: effects of particle shape.
复制标题
剪切椭圆和圆盘的动力学：颗粒形状的影响。
DOI：
10.1103/physrevlett.112.148301
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发表时间：
2013
影响因子：
8.6
通讯作者：
R. Behringer
中科院分区：
文献类型：
--
作者：
Somayeh Farhadi;R. Behringer
最近的许多努力都集中在球形颗粒的玻璃态和干扰特性上。我们对非球形粒子的这种现象知之甚少，我们通过研究椭圆迈出了第一步。我们发现受到连续库埃特剪切作用的圆盘和二维椭圆的动力学和结构特性之间存在重要差异。特别是，椭圆在平均速度、局部密度、取向顺序和局部应力方面表现出缓慢的动力学演化，而在圆盘中没有对应物。从无堵塞状态开始，椭圆首先会在剪切作用下发生堵塞，然后慢慢解除堵塞。缓慢的解除干扰过程被理解为它们的方向逐渐变化的结果，导致更密集的堆积。对于圆盘来说，粒子的旋转仅有助于摩擦力的松弛，因此不会显着引起结构变化。对于剪切堵塞状态，以应力雪崩形式发生的应力的整体建立和松弛对于圆盘和椭圆来说在性质上是不同的，并且通过椭圆与圆盘的不同形式的速率依赖性来体现。与许多颗粒系统典型的弱速率依赖性不同，椭圆显示出对剪切速率 Ω 的幂律依赖性。
Much recent effort has focused on glassy and jamming properties of spherical particles. Very little is known about such phenomena for nonspherical particles, and we take a first step by studying ellipses. We find important differences between the dynamical and structural properties of disks and two-dimensional ellipses subject to continuous Couette shear. In particular, ellipses show slow dynamical evolution, without a counterpart in disks, in the mean velocity, local density, orientational order, and local stress. Starting from an unjammed state, ellipses can first jam under shear, and then slowly unjam. The slow unjamming process is understood as a result of gradual changes in their orientations, leading to a denser packing. For disks, the rotation of particles only contributes to the relaxation of frictional forces, and hence, does not significantly cause structural changes. For the shear-jammed states, the global building up and relaxation of stress, which occurs in the form of stress avalanches, is qualitatively different for disks and ellipses, and is manifested by different forms of rate dependence for ellipses versus disks. Unlike the weak rate dependence typical for many granular systems, ellipses show power-law dependence on the shearing rate Ω.