Institute for Solid State Physics and Optics, Wigner Research Center for Physics, Hungarian Academy of Sciences, P.O. Box 49, H-1525 Budapest, Hungary.
Physique et Mécanique des Milieux Hétérogènes, PMMH UMR 7636, ESPCI-CNRS-Université Paris-Diderot-Université Pierre-et-Marie-Curie, 10 rue Vauquelin, 75005 Paris, France.
Phys Rev E. 2017 Dec;96(6-1):062903. doi: 10.1103/PhysRevE.96.062903. Epub 2017 Dec 4.
We study the rheology of dense granular flows for frictionless spherocylinders by means of 3D numerical simulations. As in the case of spherical particles, the effective friction μ is an increasing function of the inertial number I, and we systematically investigate the dependence of μ on the particle aspect ratio Q, as well as that of the normal stress differences, the volume fraction, and the coordination number. We show in particular that the quasistatic friction coefficient is nonmonotonic with Q: from the spherical case Q=1, it first sharply increases, reaches a maximum around Q≃1.05, and then gently decreases until Q=3, passing its initial value at Q≃2. We provide a microscopic interpretation for this unexpected behavior through the analysis of the distribution of dissipative contacts around the particles: as compared to spheres, slightly elongated grains enhance contacts in their central cylindrical band, whereas at larger aspect ratios particles tend to align and dissipate by preferential contacts at their hemispherical caps.
我们通过 3D 数值模拟研究了无摩擦球形-柱形颗粒密集流的流变学特性。与球形颗粒的情况一样，有效摩擦系数μ是惯性数 I 的增函数，我们系统地研究了 μ 对颗粒纵横比 Q 的依赖关系，以及对法向应力差、体分数和配位数的依赖关系。我们特别表明，准静态摩擦系数与 Q 呈非单调关系：从 Q=1 的球形情况开始，它首先急剧增加，在 Q≃1.05 左右达到最大值，然后缓慢减小直到 Q=3，在 Q≃2 时超过其初始值。我们通过分析颗粒周围耗散接触的分布，对这种意外的行为提供了微观解释：与球体相比，略微拉长的颗粒在它们的中央圆柱形带中增强了接触，而在更大的纵横比下，颗粒倾向于通过在半球形帽上的优先接触来对齐和耗散。
