| Summary: | 碩士 === 國立中央大學 === 機械工程學系 === 103 === This thesis studies dynamic behavior of spherical and non-spherical particles in a qusi-2D rotating drum by using discrete element method (DEM) simulation. The purpose of this study is to investigate the effect of particle shape on the flow behavior of granular materials. Five kinds of particles with different shapes, namely spherical, cylindrical, ellipsoidalⅠ(aspect ratio of 1.5), ellipsoidalⅡ (aspect ratio of 2.0) and paired particles, are selected and made up of spherical elements by using multi-sphere method. The transport properties, including the local average velocities, local fluctuation velocities, granular temperatures, fluctuation velocity distributions and self-diffusion coefficients, were calculated for investigating the shape effect. The numerical results show that the distributions of fluctuation velocity in the transverse and rotational directions are very close to the Maxwellian distributions, and that the cylindrical particles exhibit the most uniform velocity distribution. The total and translation granular temperatures are almost equal, indicating that the flow behavior is not dominated by particle rotation but particle translation. The particle shape effect leads to the differences in the magnitude and distribution of the granular temperatures. The mean square diffusive displacements and rotations increase linearly with time. In the diffusive rotations, spherical and ellipsoidalⅡ particles respectively produce the largest and smallest self-diffusion coefficients. The stream-wise velocity along with depth shows a mixed velocity profile for the five kinds of particles, and the maximum shear rate occurs beneath the flowing surface (about four times particle diameter in depth). The ellipsoidalⅡ particles exhibit the highest shear rate, whereas the cylindrical particles exhibit the lowest shear rate. The paired particles have the strongest inter-locking effect, hence inducing the largest dynamic angle of repose.
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