Department of Civil and Environmental Engineering, Politecnico di Milano, 20133 Milano, Italy.
Soft Matter. 2019 Sep 18;15(36):7173-7178. doi: 10.1039/c9sm01372e.
Geophysical flows that involve the transport of grains and the shearing of colloids and non-Brownian suspensions often take place above a substrate composed of the same particles that can be incorporated into the flow. Despite the importance of understanding such erodible beds to the phrasing of appropriate boundary conditions for the solution of continuum models, a rigorous definition of the erodible bed and the constitutive relations for the stresses within it are still lacking. Here, we use discrete-element simulations to show that the intense, intermittent forming and breaking of contact chains marks the transition to the erodible bed at a critical solid volume fraction, as in shear jamming of steady, homogeneous flows. However, the compressible, collisional flow that confines the bed is not strong enough to insure the stability of the contact network, resulting in a bulk stiffness that is three orders of magnitude less than in shear jamming.
涉及颗粒输运和胶体及非布朗悬浮液剪切的地球物理流动通常发生在由可纳入流动的相同颗粒组成的基底之上。尽管了解这种可侵蚀床对于连续体模型解的适当边界条件的表述很重要，但对于可侵蚀床的严格定义以及其中的应力本构关系仍然缺乏。在这里，我们使用离散元模拟表明，在临界固相体积分数下，接触链的强烈、间歇形成和断裂标志着向可侵蚀床的转变，就像稳态、均匀流动的剪切堵塞一样。然而，限制床层的可压缩、碰撞流还不够强，无法确保接触网络的稳定性，导致体弹性模量比剪切堵塞低三个数量级。
