Numerical Analysis of Dense Phase Particulate Flow using Special Computer for Particle Model (MD GRAPE)

为了考察颗粒模型(GRPE)专用计算机的性能，对非重力和真空条件下颗粒运动进行了数值计算。所有单个粒子都带电了。库仑力作用于粒子。在离散粒子模拟中，通常考虑相邻粒子之间的粒子-粒子相互作用。然而，在处理库仑力时，必须考虑远距离粒子的影响。在这种情况下，人们期待着专用计算机(GRPE)的巨大能力。本工作发现，随着颗粒数量的增加，葡萄的作用能力显著增强。此外，我们还开发了一种有效处理颗粒接触的方法。将该方法与GRAPE相结合，可以进一步减少计算时间。在上述研究的基础上，我们开发了一种计算静电影响下的粒子运动的算法。我们尝试通过平均远距离粒子对所考虑的粒子的影响来进行近似处理。这些区域被分成几个小细胞，其中存在几个粒子。当考虑电池中的粒子对远离电池的粒子的影响时，对电池中所有粒子的电荷求和，并基于求和的电荷计算由于这些粒子组装而作用在远处粒子上的力。我们称这种方法为“分组方法”。根据如何获得颗粒集合的重力点，考虑了几种分组方法。研究了分组方法计算结果的差异，并对二维和三维计算之间的关系、非球度的影响等情况进行了研究，以扩大离散粒子模拟的适用性。

Numerical calculation of particle motion under the conditions of nongravity and vacuum was performed to investigate the performance of special computer for particle model (GRAPE). All individual particles are charged. The Coulomb force acts on particles. Usually, the particle-particle interaction is considered between neighboring particles in discrete particle simulation. However, the effect of remote particles must be considered when dealing with the Coulomb force. The great ability of the special computer (GRAPE) is expected in such circumstances. It was found in the present work that significant ability of GRAPE is manifested as the number of particles increases. Moreover, we developed a method for efficient treatment of contact of particles. By combining this method with GRAPE,the computation time can be further reduced.Along with the above study, we developed an algorithm to calculate particle motion influenced by static electricity. We attempted an approximate treatment by averaging the effects of remote particles on a particle considered. The regions is divided into small cells in which several particles exist. When considering the effect of particles in a cell on a particle far from the cell, electric charge of all particles in the cell is summed and the force acting on the remote particle due to the assembly of these particles is calculated based on the summed charge. We call this method "grouping method." Several grouping methods were considered depending on how to obtain the gravitational point of the assembly of particles. In this work, the difference in calculated results between grouping methods was studied.Also, to enlarge applicability of the discrete particle simulation, various cases were investigated : the relation between the 2D and 3D calculations, the effects of non-sphericity and so on.