Gómez Leopoldo R, Turner Ari M, Vitelli Vincenzo
Department of Physics and Instituto de Física del Sur, Universidad Nacional del Sur-CONICET, Av L.N. Além 1253. (8000), Bahía Blanca, Argentina.
Phys Rev E Stat Nonlin Soft Matter Phys. 2012 Oct;86(4 Pt 1):041302. doi: 10.1103/PhysRevE.86.041302. Epub 2012 Oct 8.
The confining pressure P is perhaps the most important parameter controlling the properties of granular matter. Strongly compressed granular media are, in many respects, simple solids in which elastic perturbations travel as ordinary phonons. However, the speed of sound in granular aggregates continuously decreases as the confining pressure decreases, completely vanishing at the jamming-unjamming transition. This anomalous behavior suggests that the transport of energy at low pressures should not be dominated by phonons. In this work we use simulations and theory to show how the response of granular systems becomes increasingly nonlinear as pressure decreases. In the low-pressure regime the elastic energy is found to be mainly transported through nonlinear waves and shocks. We numerically characterize the propagation speed, shape, and stability of these shocks and model the dependence of the shock speed on pressure and impact intensity by a simple analytical approach.
围压P可能是控制颗粒物质性质的最重要参数。在许多方面，强压缩颗粒介质是简单的固体，其中弹性扰动以普通声子的形式传播。然而，随着围压降低，颗粒聚集体中的声速持续下降，在堵塞-解堵塞转变时完全消失。这种反常行为表明，低压下的能量传输不应由声子主导。在这项工作中，我们使用模拟和理论来展示颗粒系统的响应如何随着压力降低而变得越来越非线性。在低压 regime中，发现弹性能量主要通过非线性波和激波传输。我们通过数值方法表征了这些激波的传播速度、形状和稳定性，并通过一种简单的分析方法对激波速度对压力和冲击强度的依赖性进行了建模。
