散粒体组构特征对系统自组织临界性的影响

为验证散粒体崩塌中的自组织临界现象是否是一种有限尺度效应,自组织临界现象的发生终究由系统的尺寸还是系统的组织原则来确定,进行了均匀和非均匀散粒体崩塌的实验.实验证明影响系统自组织临界性的关键内因应为系统组构特征而并非前人所认为的组元尺度或系统规模.进而采用离散单元法对均匀和非均匀砂堆的应力传递和分布状况进行了数值模拟,从孔隙率、配位数和信息熵三个指标的比较来看,非均匀散粒体系统内部颗粒之间相互充填更充分,应力分布和传递状况更趋复杂,从而系统结构更具稳定性,系统呈现自组织临界性.同时,模拟结果表明,二者应力传递路径的分维值并无明显差别,说明分形结构目前尚不能作为系统自组织临界性质的判据.

Influence of the Buildup Charactoristics of Granular Mixtures on It's Self-organized Criticality

Physics experiments on large scale uniform and non-uniform granular mixtures avalanche were carried out and the results proved that internal cause of SOC effect was most probably the structure characteristics of the system but not the size of granular or the scale of system. Furthermore, the stress transmission and stress distribution of uniform and non-uniform granular mixtures were simulated with discrete element method. According to the contrast between uniform and non uniform granular mixtures from three parameters of Shannon entropy, porosity and coordination number,it was found that the stuffing of granular matter in the non uniform granular system is more sufficient, so the system is more stable and it can show SOC. Meanwhile, there is no distinct difference of fractal dimension between the uniform and non uniform granular mixtures and thus the fractal could not be thought as the criterion of SOC.