无粘性颗粒材料的环形剪切：从惯性到准静态
Annular shear of cohesionless granular materials: from inertial to quasistatic regime
摘要：
使用离散模拟，我们研究了模型颗粒材料在环形剪切单元内的行为。具体地说，二维组件的磁盘被放置在两个圆形壁之间，内一个以规定的角速度旋转，而外一个可以膨胀或收缩，并保持恒定的径向压力。专注于稳态流动，我们划定在参数空间的适用范围最近推出的剪切颗粒材料的本构关系（基于惯性数）。我们讨论了两个来源的更强的应变率观察到的内边界附近，附近的壁和不均匀的应力场的库埃特细胞。在一定速度以上，在内壁附近形成惯性区域，对于足够小的应力梯度，已知的本构关系适用于该惯性区域，并且由于壁滑移而进行适当的校正。远离内壁，缓慢的，显然是无界蠕变发生在名义上固体材料，虽然它的密度和剪应力与法向应力的比值是在临界值的堵塞侧。除了流变特性，我们的模拟提供了微观信息的接触网络和速度波动，这是潜在的有用的评估理论方法。
英文摘要：
Using discrete simulations, we investigate the behavior of a model granular material within an annular shear cell. Specifically, two-dimensional assemblies of disks are placed between two circular walls, the inner one rotating with prescribed angular velocity, while the outer one may expand or shrink and maintains a constant radial pressure. Focusing on steady state flows, we delineate in parameter space the range of applicability of the recently introduced constitutive laws for sheared granular materials (based on the inertial number). We discuss the two origins of the stronger strain rates observed near the inner boundary, the vicinity of the wall and the heteregeneous stress field in a Couette cell. Above a certain velocity, an inertial region develops near the inner wall, to which the known constitutive laws apply, with suitable corrections due to wall slip, for small enough stress gradients. Away from the inner wall, slow, apparently unbounded creep takes place in the nominally solid material, although its density and shear to normal stress ratio are on the jammed side of the critical values. In addition to rheological characterizations, our simulations provide microscopic information on the contact network and velocity fluctuations that is potentially useful to assess theoretical approaches.
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