The porous structure of ultra-fine powder beds, the porosity ratio of which is more than 90%, was constructed by the simulation of aggregate packing. The various aggregates of ultra-fine powders were obtained by the extended DLA model. The aggregating process was analyzed by Smoluchowski's equation, and the aggregate structure was discussed quantitatively with fractal dimensionality. The simulation had some adverse effects on the aggregation, when the length of the side of the simulated space was smaller than the critical value. The critical values of the length were 180 and 50 times the particle diameters, respectively for two and three dimensional cases. As the mean number of particles in a single aggregate increased, the width of the packing simulation space must be increased to reproduce the actual shape of pore size distribution in the packed bed. If the mean number of particles in a single aggregate is more than 100, for example, the width required is more than 200 times the particle diameter both for two and three dimensional cases. The effect of adhesion between aggregates on packed bed structure decreased as the size of aggregate increased, because the bridging among several aggregates created large voids.

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Variation in the molecular weight distribution of straight polymers, with a mean molecular weight of (1.1-2)×10⁶, upon central, random, or terminal chain scisson was simulated. The peak in the molecular weight distribution was shown to shift to a lower molecular weight upon central or random chain scisson, and the randomly cut polymers were more widely distributed than the centrally cut polymers. A bimodal distribution was obtained upon terminal chain scisson. A parameter “n₁” in a Rosin-Rammler plot, where molecular weight was substituted for particle size, stayed nearly constant for large t values duning central and random chain scisson. This constant n₁ value was 2. 1-2.3 for central chain scisson and 1.3-1.7 for random chain scisson. n₁ for terminal chain scisson decreased to zero with increasing t. The application of these simulation results to ball-milling of polyvinylpyrrolidone (PVP) in nitrogen showed that the terminal chain scisson of PVP was accompanied by its random chain scisson. It was also shown that the addition of phenothiazine or acridine increased the rate of random chain scisson.

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In this paper, a model of cement particle injection into the ground is proposed by considering the interaction between the adhesion of a cement particle and the drag force caused by air.
Pressure loss by accumulated of packed cement particles in a pipe is simulated by the Distinct Element Mehod (DEM), and a criteria for ensuring the satisfactory injection is presented.

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The distinct element method (DEM) is a very effective analytical tool for the problem of granular materials. In the previous papers it was indicated that the complex behavior of the granular materials during disharge in silos can be properly simulated using DEM. In order to explain the dynamic variation of the pressures to the side walls during discharge, a problem of 4000 granular elements is analyzed, and the behavior of the particles and the variation of the pressures on the walls are examined in detail. As a result of this study, a pulsation phenomenon, like the experimental one, is observed, and the period of this phenomenon is almost the same as that of the fluctuation in the pressures. It is important to explain the period of this phenomenon, so the approximate elastic velocity and the variation of the void ratio are examined. However, the appropriate relationship between these parameters cannot be found.

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Numerical modeling of convection of powder was done. Convection of powder occurs when a strong vertical vibration is applied. When the control parameter, the acceleration amplitude Γ, exceeds some critical value Γ_c, convection and heaping start. In our simulation, the powder is modelled with a discrete elementary method but without rotation and with isotropic linear elastic interaction. The convection is reproduced, and Γ_c turns out to be about the gravity acceleration g, which agrees with the experiment, an other remarkable phenomena, surface fluidization, is also reproduced, and the critical value Γ_c again agrees with the experiment. It is suggestde that this convection is caused by the instability of the powder induced by the elastic interaction.

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Chain-like clustering of 3μm Sio₂ particles was investigated by Monte Carlo simulation along with the experiment. The magnetic force was applied in parallel to the particle layer suspended in a thin film of magnetic fluid. The size distribution of chain-like clusters was measured in relationship to the coverage c or the bulk-mean area fraction of particles: k=90c^1.38 The agreement between the computer simulation and the experiment was fairly good. Particle movement from the initial to final equilibrium positions was also measured for all particles. Monte Carlo simulation was foud to underestimate the particle movement in the region of high particle concentration.

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Physical experiments and numerical simulations were performed to find under what conditions the formation of arches plugging the flow of granular materials are likely to occur throughout the gravity emptying of a silo. In the laboratory measurements, the movement of particle was characterized with the help of a video camera, and wall stress was measured by strain gauges. For computer simulation of this issue, the Discrete Element Method, specifically taking into account of rolling friction effect, was used. The results of numerical simulations by the Discrete Element Method were in good agreement with the experimental measures not only in the flow pattern but also in the formation of arches and wall stress.

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Chute flow of spherical particles is numerically simulated by applying a particle element method, PEM. The calculated velocity distributions of flowing particles agree well with the measured ones, and it is confirmed that the particle element method is a useful tool for the simulation of the flow of granular materials. The microscopic state variables, porosity and dissipation energy distributions in the flow of granular materials, can be obtained by this simulation. The relationships between the velocity distributions and these state variables are discussed. These state variables are important factors in understanding the mechanical behavior of granular materials.

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