Perrin Hugo, Wyart Matthieu, Metzger Bloen, Forterre Yoël
Aix Marseille University, CNRS, IUSTI, 13453 Marseille, France.
Institute of Physics, Ecole Polytechnique Fédérale de Lausanne, CH-1015 Lausanne, Switzerland.
Phys Rev Lett. 2021 Jun 4;126(22):228002. doi: 10.1103/PhysRevLett.126.228002.
The jamming transition is accompanied by a rich phenomenology such as hysteresis or nonlocal effects that is still not well understood. Here, we experimentally investigate a model frictionless granular layer flowing down an inclined plane as a way to disentangle generic collective effects from those arising from frictional interactions. We find that thin frictionless granular layers are devoid of hysteresis of the avalanche angle, yet the layer stability increases as it gets thinner. Steady rheological laws obtained for different layer thicknesses can be collapsed into a unique master curve, supporting the idea that nonlocal effects are the consequence of the usual finite-size effects associated with the presence of a critical point. This collapse indicates that the so-called isostatic length l^{*}, the scale on which pinning a boundary freezes all remaining floppy modes, governs the effect of boundaries on flow and rules out other propositions made in the past.
阻塞转变伴随着丰富的现象学特征，如滞后现象或非局部效应，目前人们对这些现象仍未完全理解。在此，我们通过实验研究了一个沿倾斜平面流动的无摩擦颗粒层模型，以此来区分一般的集体效应与摩擦相互作用产生的效应。我们发现，薄的无摩擦颗粒层不存在雪崩角的滞后现象，但其层稳定性会随着厚度变薄而增加。针对不同层厚得到的稳态流变学定律可以合并为一条独特的主曲线，这支持了非局部效应是与临界点存在相关的常见有限尺寸效应的结果这一观点。这种合并表明，所谓的等静长度(l^{*})，即固定边界会冻结所有其余软模的尺度，控制着边界对流动的影响，并排除了过去提出的其他观点。
