粒度分布をもつ粉体のランダム充てん過程のシミュレーションとその充てん構造の解析

抄録

In this study computer simulation was carried out to make randomly packed beds of powder with a particle size distribution, and to analyze the internal structures formed. The simulation of the packing process had two kinds of boundary condition, the fixed and the periodic one, and the particle size distribution was assumed to be discrete Forsfield’s distribution consisting of five different size spheres which can make the most dense packing in the geometrically regular arrangement of spheres.
The results are summarized as follows:
(1) In the packed bed larger spheres are uniformly dispersed, while smaller ones unevenly fill up gaps made by larger ones.
(2) In case of the packing into a container with fixed walls, abrupt lowering of the density of packing is obtained near the walls and corners leading to the loose packing structure there.
(3) In the process of random packing, larger particles having a large volume fraction build up the fundamental structure, while smaller ones rolling down through the gaps among larger ones to the stationary positions contribute to the increment of the density with the lapse of time.
(4) For the random packing of the powder with such a particle size distribution the mean density is strongly influenced by the packing state of larger particles with a large volume fraction, while both the distribution and the mean value of coordination number are dependent upon the packing state of smaller particles with a large fraction in number.
(5) Under the periodic boundary condition excluding a wall effect, the mean values of the packing density and the coordination number were 0.622 and 5.92, respectively.