科研之友
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摘要
The motion of rigid particles driven by gravity in a viscous fluid is relevant in many natural and industrial processes, and many investigations have been carried out on spheroidal particles. However, many non-spherical particles with complex surface structure exist in nature. So far, only few people have proposed an effective particle-laden flow model for practical engineering applications. Therefore, we put forward a set of models combined with the realistic shape data for practical engineering simulation. We present a systematic approach by researching the three-dimensional sedimentation of realistic shaped particles in a viscous fluid. The DEM-FDM method is used for numerical simulations. The morphology of particles is obtained by micro X-ray computed tomography. The novelty of our present contribution relies on the combination of the Monte Carlo Scheme with FDM to calculate the hydrodynamic force acting on the particles. In addition, a new procedure is proposed using overlapping spheres to reconstruct the particles' micro-morphology in three dimensions. We verify the numerical implementation of our approach and validate it against the analytical solution for ellipsoids in uniform shear flow derived by Jeffery, 1922. We investigate the sedimentation of realistic shaped particles separately and that of four particles with different morphologies in an incompressible fluid. The aspect ratio (AR) ranges from 1.2 to 2.2. The density ratio is 2.6. The results show that the path instability of sedimentation of realistic shaped particles with different morphologies occurs, but the behaviour of their sedimentation is closely related to the particles' AR. The sedimentation velocity of particles with sharp corners is obviously higher than that of flat particles, which have a relatively lower sphericity. For particles with higher AR, the phenomenon of 'helical sedimentation' appears. This paper provides an effective method to simulate the interactions of particles and their morphology in an incompressible fluid in engineering applications, with continuous improvements in computer performance.
