The effect of the particle interactions in the sedimentation process
Description
The Lattice Boltzmann Method (LBM) is adopted to numerically simulate the particle sedimentation process under three conditions: particles settling in an infinite vessel with initial homogenous configuration, particles settling in an inclined vessel and bidisperse sedimentation The sedimentation process of solid particles in a two-dimensional channel with an initially homogeneous, square configuration is investigated at Reynolds numbers up to 10. The simulations show that the process of sedimentation encompasses three stages. In the first stage, the initial particle configuration plays a major role on the average velocity of the particles. During the second stage, the concentration is lower, strong particles interactions occur and the formation and destruction of particle clusters play a major role in the process. During the third stage, the concentration becomes low and the particle clusters are stable. The wakes generated by particle and clusters, especially of the leading cluster becomes important in the process During the sedimentation process in inclined tubes, the LBM simulations show the trajectories and flow behavior of individual particles, particle-particle and particle-wall interactions as well as the formation of particle clusters. The global convection motion that was experimentally observed during such processes and, which tends to enhance the sedimentation process is reproduced numerically The monodisperse and bidisperse sedimentation, where pairs of particle are place in an equal vertical distance, are also investigated by the LBM. In the bidisperse sedimentation, when pairs of particles are placed dense enough, a flow channel will occur in the central part of the container, which is called the channelization. As long as the flow channel is established, the particles motions are periodic. The trajectories of the pair particles' horizontal displacements are similar to the profiles of the Lorenz equations. The trajectories of the monodisperse sedimentation, the bidisperse sedimentation with the channelization, the bidisperse sedimentation without channelization and a simple bidisperse sedimentation, are related to the Lorenz equations of Category-1 where a butterfly profile occurs, Category-2 where a trajectory will fall into a stable periodic orbit, Category-3 where an unstable attractor occurs and Category-4 where a trajectory is attracted to the origin point, respectively