Scale-free channeling patterns near the onset of erosion of sheared granular beds
Scale-free channeling patterns near the onset of erosion of sheared granular beds
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DOI：
10.1073/pnas.1609023113
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发表时间：
2016-10-18
影响因子：
11.1
通讯作者：
Wyart, Matthieu
中科院分区：
文献类型：
--
作者：
Aussillous, Pascale;Zou, Zhenhai;Wyart, Matthieu
侵蚀塑造了我们的景观，当流体对沉积层施加足够的剪切应力时，就会发生侵蚀。是什么在微观层面上控制侵蚀仍然存在争议，特别是在临界点附近，迫使它停止。在这里，我们研究，实验，集体动力学的移动粒子，使用一个设置，系统自发地演变对侵蚀发病。研究发现，侵蚀通量的空间组织在空间上是不均匀的，它沿着局部通量σ的通道分布，在阈值附近呈标度分布，遵循P（sigma）近似于J/sigma的规律，其中J是平均侵蚀通量。通道在强迫方向上有很强的相关性，但在横向上没有。我们表明，这些结果定量同意的模型，其中的动力学是由无序（其中通道移动的粒子）和粒子相互作用（减少沟道）的竞争。这些观察结果支持，对于层流，侵蚀是一个动态的相变，与发生在肮脏的超导体的塑性脱钉过渡的相似性。我们在这里介绍的方法也可以应用于探测这些系统。
Erosion shapes our landscape and occurs when a sufficient shear stress is exerted by a fluid on a sedimented layer. What controls erosion at a microscopic level remains debated, especially near the threshold forcing where it stops. Here we study, experimentally, the collective dynamics of the moving particles, using a setup where the system spontaneously evolves toward the erosion onset. We find that the spatial organization of the erosion flux is heterogeneous in space and occurs along channels of local flux sigma whose distribution displays scaling near threshold and follows P(sigma)approximate to J/sigma, where J is the mean erosion flux. Channels are strongly correlated in the direction of forcing but not in the transverse direction. We show that these results quantitatively agree with a model where the dynamics is governed by the competition of disorder (which channels mobile particles) and particle interactions (which reduces channeling). These observations support that, for laminar flows, erosion is a dynamical phase transition that shares similarity with the plastic depinning transition occurring in dirty superconductors. The methodology we introduce here could be applied to probe these systems as well.