Numerical analysis of fine powder flow using smoothed particle method and experimental verification

Abstract

Numerical simulation of velocity and stress fields for flowing powder composed of an infinite number of particles presents a most difficult problem in powder technology. The distinct element method (DEM) is useful for determining each particle trajectory which involves multi-body interactions. However, total particle cannot be computed using DEM. The particle number which can be calculated for a three-dimensional spherical system would be in hundreds of thousands. A description of flow characteristics for a small amount of powder would not be practical. Simulation within a tank would thus be virtually impossible. The authors have conducted numerical simulation of flowing powder using the smoothed particle (SP) method through application of continuum dynamics. The authors’ group is the first to contrive to apply this method to powder flows. In the SP method, partial differential equations that govern flow fields are transformed to ordinary differential equations of the Lagrangian-type for particle motion. Numerical analysis of ordinary differential equations is much simpler compared to partial differential equations. Lagrangian analysis is suitable for determining the characteristics of discrete particles. The equation of powder pressure exerted on tank bed due to differences in density and constitutive equations that consider yield stress have been used as basic equations and the latter were obtained by the authors’ group using DEM. These equations provide clarification of the rheological characteristics of powder flow. Glass beads (particle diameter: 100 μm ) were used in the present study as test powder stored in a tank and discharged by gravitational force. Calculated velocity distribution, free surface in the tank and the rate of discharge were compared with experimental data and a good agreement was noted. Based on the results of this study, the SP method in conjunction with the model equation for yield stress appears quite useful for simulating the flow of fine powder.