Jakšić Z M, Vrhovac S B, Panić B M, Nikolić Z, Jelenković B M
Institute of Physics, P.O. Box 68, Zemun 11080, Belgrade, Serbia.
Eur Phys J E Soft Matter. 2008 Dec;27(4):345-56. doi: 10.1140/epje/i2008-10384-5. Epub 2008 Nov 18.
We study experimentally the creeping penetration of guest (percolating) grains through densely packed granular media in two dimensions. The evolution of the system of the guest grains during the penetration is studied by image analysis. To quantify the changes in the internal structure of the packing, we use Voronoï tessellation and a certain shape factor which is a clear indicator of the presence of different underlying substructures (domains). We first consider the impact of the effective gravitational acceleration on upward penetration of grains. It is found that the higher effective gravity increases the resistance to upward penetration and enhances structural organization in the system of the percolating grains. We also focus our attention on the dependence of the structural rearrangements of percolating grains on some parameters like polydispersity and the initial packing fraction of the host granular system. It is found that the anisotropy of penetration is larger in the monodisperse case than in the bidisperse one, for the same value of the packing fraction of the host medium. Compaction of initial host granular packing also increases anisotropy of penetration of guest grains. When a binary mixture of large and small guest grains is penetrated into the host granular medium, we observe size segregation patterns.
我们通过实验研究了二维中客体（渗流）颗粒在密集堆积颗粒介质中的蠕变渗透。通过图像分析研究了渗透过程中客体颗粒系统的演化。为了量化堆积内部结构的变化，我们使用了沃罗诺伊镶嵌和一个特定的形状因子，该形状因子是不同潜在子结构（区域）存在的明确指标。我们首先考虑有效重力加速度对颗粒向上渗透的影响。发现较高的有效重力增加了对向上渗透的阻力，并增强了渗流颗粒系统中的结构组织。我们还关注渗流颗粒的结构重排对一些参数的依赖性，如多分散性和主体颗粒系统的初始堆积分数。发现在主体介质堆积分数相同的情况下，单分散情况下的渗透各向异性比双分散情况下的大。初始主体颗粒堆积的压实也增加了客体颗粒渗透的各向异性。当大小不同的客体颗粒二元混合物渗透到主体颗粒介质中时，我们观察到了尺寸分离模式。
