The simulation of powders with liquid bridges in a 2D vibrated bed

The discrete element method is employed to study the convection cells of wet glass beads in a two-dimensional vibrated granular bed. Three types of viscous fluids with different values of viscosity are used in this work. A simplified model of dynamic bridge strength based on the superposition of lubrication and circular approximation is used in the simulation model. The flowfields of wet particles, the depth profiles of solid fraction and granular temperature as functions of the altitude are investigated. The mechanism of energy dissipation due to friction, inelasticity, viscous resistance and liquid bridge bond rupture are also discussed in detail. For wet granular materials, the liquid bridge force due to surface tension and viscosity interacts with frictional force mutually to determine the strength of the convection flow rate. The energy dissipation is mainly associated with the viscous force, the interparticle friction and the inelasticity of collision, rather than with the capillary force of liquid bridge. The energy dissipation increases monotonously with the increase of the dimensionless interstitial liquid volume, and the distributions of the energy dissipation are strongly influenced by the properties of viscous fluids. Plotting the energy dissipation against the dimensionless liquid volume in a logarithmic scale, a power law relation is shown to exist between the energy dissipation and the dimensionless liquid volume. (C) 2001 Elsevier Science Ltd. All rights reserved.