The Numerical Simulation And Experiment Research Of Wet Particles Flow In A Hopper

In the industrial process the material in the hopper always contains some water. With the aid of liquid bridge model, DEM(Discrete Element Method) and mathematical models, this paper firstly simulates the flow of wet particles in a hopper to study the influence of liquid bridge on the flow patterns and flow rate.In order to calculate liquid bridge force and indirectly determine the half fill angel, an iterative method was adopted. Liquid bridge force was acquired successfully.Concerning the selection of simulation parameters, a new method was applied: That is estimating the drop of a particle from a fixed height to a plane to determine the critical time step.The research r esults show: Comparing with dry granular flow, wet granular materials' flow rates reduce greatly. Meanwhile the influences of a hopper structure on the flow patterns of wet materials are different from dry materials. Usually the critical open diameter of a hopper for dry particles is more than 3 times of particle diameter, but not less than 4 times for wet particles. For dry particles, the hopper angle which causes transformation from funnel flow into mass flow is about 45? while for wet particles it is about 40? Moreover the effect of liquid bridge on small particles is more obvious than on big particles. With the same water content small particles are easier to aggregate than big particles. When the water content increases, the motion of small particles i s obstructed evidently, and the flow rate drops greatly. But the flow rate of big wet particles rises first drops afterwards. In order to examine the results of simulations, some experiments in two-dimensional(2D) hopper were carried out. The simulation results agreed well with the experimental results.