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

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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.