Study of surface deformation of granular material due to flow and vibration toward the development of mesoscopic physics

如果考虑宏观性质，颗粒材料可视为连续体。另一方面，在材料的边界附近，离散性质是必不可少的。本研究的目的是建立一种新的物理学，弥合宏观和微观图像之间的差距。通过垂直振动的干颗粒材料的实验，阐明了当层数（微观）超过3层时，可以产生类似于弹性材料或流体中所观察到的集体运动，但它们的行为是由层深（宏观）表征的。此外，固体状和流体状域被发现共存，并在时空上相互变化，形成波动。在颗粒物质暴露于粘性流，我们已经表明，相当小的颗粒分布的不均匀性可以通过颗粒的重排和流动集中产生宏观滑坡。

Granular materials can be regarded as continua, if macroscopic properties are concerned. On the other hand, discrete properties are essential near the boundary of the materials. The purpose of the present research is to establish a new physics that bridges the gap between the macroscopic and microscopic pictures. By the experiments using a vertically vibrated dry granular material, we have elucidated that the collective motions similar to the ones observed in elastic material or fluid can be generated if the number of layer (microscopic view) exceeds 3, but that their behaviors are characterized by the layer depth (macroscopic view). Moreover, the solid-like and fluid-like domains are found to co-exist and change to each other spatiotemporally to form wave motions. In the granular material exposed to viscous flows, we have shown that quite a small inhomogeneity of particle distribution can generate macroscopic landslides via rearrangement of particles and the flow concentration.