Very recently, To et al. have experimentally explored granular flow in a cylindrical silo, with a bottom wall that rotates horizontally with respect to the lateral wall [Phys. Rev. E 100, 012906 (2019)]. Here we numerically reproduce their experimental findings, in particular, the peculiar behavior of the mass flow rate $Q$ as a function of the frequency of rotation $f$. Namely, we find that for small outlet diameters $D$ the flow rate increased with $f$, while for larger $D$ a nonmonotonic behavior is confirmed. Furthermore, using a coarse-graining technique, we compute the macroscopic density, momentum, and the stress tensor fields. These results show conclusively that changes in the discharge process are directly related to changes in the flow pattern from funnel flow to mass flow. Moreover, by decomposing the mass flux (linear momentum field) at the orifice into two main factors, macroscopic velocity and density fields, we obtain that the nonmonotonic behavior of the linear momentum is caused by density changes rather than by changes in the macroscopic velocity. In addition, by analyzing the spatial distribution of the kinetic stress, we find that for small orifices increasing rotational shear enhances the mean kinetic pressure $\langle p^k\rangle$ and the system dilatancy. This reduces the stability of the arches, and, consequently, the volumetric flow rate increases monotonically. For large orifices, however, we detected that $\langle p^k\rangle$ changes nonmonotonically, which might explain the nonmonotonic behavior of $Q$ when varying the rotational shear.

中文翻译：

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旋转剪切作用下筒仓中的颗粒流速

最近，To等人。在实验中，人们探索了圆柱形筒仓中的颗粒流，其底壁相对于侧壁水平旋转[ Phys。启ë 100，012906（2019）]。在这里，我们以数值方式重现了他们的实验发现，特别是质量流率的特殊行为$问$ 作为旋转频率的函数 $F$。即，我们发现对于较小的出口直径$d$ 流速随着 $F$，而较大的 $d$确认非单调行为。此外，使用粗粒度技术，我们可以计算宏观密度，动量和应力张量场。这些结果最终表明，排出过程的变化与从漏斗流到质量流的流型变化直接相关。此外，通过将孔口处的质量通量（线性动量场）分解为宏观速度和密度场这两个主要因素，我们得出线性动量的非单调行为是由密度变化而不是宏观速度的变化引起的。此外，通过分析动应力的空间分布，我们发现对于小孔口，增加旋转剪切力会提高平均动压力$〈p^{ķ}〉$和系统扩张。这降低了拱形的稳定性，因此，体积流量单调增加。但是，对于大孔口，我们检测到$〈p^{ķ}〉$ 非单调变化，可能解释了 $问$ 当改变旋转剪切力时。