Incipient Motion Of A Single Particle In The Stirred Tank-Experiments And Simulations

The incipient motion of particles is widespread in nature,such as the transfer of riverbed sediments, particle bed erosion, dune formation. It is the theoretical basis for the study of sediment transport, and the initial stage of solid particle suspension in the stirred tank. In recent years, more scholars have studied the incipient motion under laminar flow conditions. This paper will continue to explore the incipient motion characteristics of the particles under laminar flow conditions on the basis of predecessors.In this paper, I studied the incipient motion of the single particle on the regular substrate in the square stirred tank with Rushton turbine.The substrate is composed of the identical glass spheres with triangular arrangement. At the end of the experiment, the kinematic trajectories and velocity of the particles are obtained by Matlab program. In addition, this paper combines the LBM method to simulate the experimental operating conditions, and obtains the trajectories of the particles, the force situation and the detailed information of the surrounding flow field. The results show that: (1) The movement of the particles on the substrate is predominantly in a rolling state about 76%, and the particles move along the gap of the substrate, rarely across the top of the particles on the substrate; (2) The critical initial rotational speed increases with the particle density. When the particle density ratio is 2.26 ?3.36,the trajectory is the same. When the density ratio is 7.98 ?11.49, the trajectory is different from that of the former (3) The diameter of the particles changes the burial degree. When the diameter ratio of the particles to the substrate less than 0.5, burial degree significantly increase and require high initial rotational speed; (4) When the incipient position y/T of the particles is the same, the distributions of the critical Shields corresponding to different x/T are still symmetrical about the y-axis, although the flow patterns are different; (5)Based on the LBM simulation, The simulated and the experimental error of the critical suspension speed is about 3%,The simulated values of the particle trajectories are in good agreement with the experimental data; (6) When Re<30, the movement of the particles on the substrate is mainly affected by the horizontal force of the fluid. The contribution of the horizontal force of the fluid is about 75%, followed by the moment of the fluid about 25%, and the lift is negligible. Substrate.