Formation and Collapse of Cavity Network in a Granular Material due to Viscous Flow and Vibration

1.我们进行了实验，发现在一个否则均匀的颗粒材料的空腔区域的存在下，该空腔周围的局部流场产生很大的影响。局部增强了孔洞边界处的应力，导致孔洞的坍塌。我们已经开发了一个数值模拟，可以令人满意地解释我们的实验结果。此外，我们扩展我们的数值模拟，以便处理三维空腔。这些结果可应用于暴雨时滑坡的预测，以及预测地下水流中污染物通过空腔网络的快速对流，以及人体肝脏肿瘤细胞周围血管生成的新技术.我们研究了涟漪和巴坎沙丘的产生，由于粘性流的颗粒材料的表面。这些结果对海湾地区沙漠扩展的预测和海底水位的控制具有一定的指导意义.对涡环与颗粒表面的碰撞进行了实验研究。我们检查了涡环强度对冲击时颗粒层上留下的雕刻图案的依赖性。4.薄层颗粒状物质垂直振动，显示出规则的多边形涟漪图案和起伏。我们阐明了这些图案的形成机制，并在同一时间得到的临界层数，显示集体运动像在连续介质中观察到的。这一现象部分可以用薄弹性层的屈曲和弯曲运动来解释。这些研究有望填补颗粒材料微观碰撞过程与宏观流体运动之间的差距，并在国际和国内重要会议上发表论文。

1. We performed experiments and found that the presence of cavity regions in an otherwise uniform granular material gives great influence on the local flow field around that cavity. The stress at the boundary of the cavity is locally enhanced, and the collapse of the latter is induced. We have developed a numerical simulation that can satisfactorily explain our experimental findings. Furthermore we extend our numerical simulation so as to deal with three-dimensional cavities. These results can be applied to the prediction of landslides at the time of heavy rainfall and a new technique to predict anomalously fast convection of contaminants in underground water flow through cavity networks, as well as angiogenesis around tumor cells in the human liver.2. We studied the generation of ripples and Barchan dunes due to viscous flow over the surface of the granular material. These results are applicable to the prediction of spread of desert area and the control of seabed level in the bay area.3. Experiments on the collision of a vortex ring on the granular surface were made. We examined the dependence of the strength of the vortex ring on the engraved patterns left on the granular layer at the impingement.4. Thin layer of granular materials were vertically vibrated, which revealed regular polygonal ripple patterns and undulations. We elucidated the mechanism of the formation of these patterns, and at the same time obtained the critical layer number that showed collective motion like those observed in continuum media. The behavior was partially explained by the buckling and bending motion of thin elastic layer. These studies are expected to bridge the gap between microscopic collision process and macroscopic fluid motion of the granular material, and our works are presented at major international conferences and domestic meetings.