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

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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