一億個オーダの離散粒子反応シミュレーションのためのモデルアルゴリズムとコード開発

虽然最近由Cundall和Strack(1979)提出的离散单元法(DEM)模拟技术的发展使颗粒物系统的数值描述取得了巨大的进步，但显而易见的是，在工业中任何现实的颗粒物系统都包含数十亿个颗粒，即使对现有的计算机来说，也几乎不可能直接对其进行模拟。针对大规模数字高程模型(DEM)模拟问题，提出了基于相似粒子集合(SPA)的大规模DEM模拟方法。该模型包括由粒子运动方程导出的组件中粒子运动的标度定律。在SPA模型中，直径、密度和化学组成相同的多个粒子的运动是Rep…更讨厌的是一种粒子，它被称为具有代表性的粒子。代表性粒子的体积与所代表粒子的体积之和相同，并且具有相同的密度和化学成分。不同颗粒在基床中的局部聚集应该保持在具有代表性的颗粒的床层中。利用SPA模型，可以使具有一定放大倍率的典型颗粒的床层流动与原始颗粒的流动相似，而计算量要小得多。SPA模型最重要的方面是，它可以应用于粘性颗粒以及尺寸不均匀的颗粒的床层。通过对具有相同性质的无粘性颗粒、两种不同密度的粘性颗粒以及放大倍数为6的粘性颗粒组成的二维床层的数值模拟，验证了模型的有效性。此外，在传统的三维DEM模拟程序中引入了颗粒尺寸分布，并对颗粒-流体相互作用力的理论建模和计算方案进行了修改。利用改进的格式对非均匀颗粒体系进行了三维数值模拟。当考虑颗粒尺寸分布时，观察到气泡具有明显的尾迹相。另一方面，在不考虑颗粒大小分布的情况下，床层表现为段塞状。较少

Although numerical description of particulate systems has recently been achieved a dramatic progress by the development of discrete element method (DEM) simulation technique originally proposed by Cundall and Strack (1979), it is evident that any realistic particulate system in industries contains billions of particles and that even for a current computer it is almost impossible to directly simulate them. The present work is a new challenge to large-scale DEMs starting from a scaling consideration on the governing equations taking into account cohesiveness and non-uniform particle properties.For large-scale DEM simulation, the "Similar Particle Assembly (SPA) Model" was proposed for large-scale DEM simulation of particulate systems. The model includes the scaling law for the motion of particles in an assembly, which is derived from the equations of motion of particles. In the SPA model the motion of multiple particles whose diameter, density and chemical composition are the same is rep … More resented by one particle, which is called a representative particle. A representative particle occupies the same volume as the sum of the volume of represented particles and has the same density and chemical composition. The local assembly of different particles in the ginal bed is supposed to be maintained in the bed of representative particles. With the SPA model the flow of the bed of representative particles of a certain magnification can be made similar to that of the original particles with a much less computation load. The most significant aspect of the SPA model is that it can be applied to beds of cohesive particles as well as particles of non-uniform sizes. The model was validated by numerical simulation of a two-dimensional bed of non-cohesive particles of equal properties, a bed of particles of two different densities and cohesive particles up to the magnification of 6.Moreover, particle size distribution was introduced into the conventional three-dimensional DEM simulation code with some modification in both theoretical modeling and computational scheme for the calculation of particle-fluid interaction force. The 3-dimensional simulation for non-uniform particle size system was carried out by using the modified scheme. The bubble with clear wake phase was observed when the particle size distribution was considered. On the other hand, the bed behavior was slugging-like when the particle size distribution was not considered. Less