CFD-DEM simulation of liquid-solid fluidized bed with dynamic restitution coefficient

Abstract

In liquid-solid fluidized beds, the existence of interstitial liquid among colliding particles generates more energy dissipation than that in the gas-solid fluidized bed. In this paper, a numerical modelling method to account for the energy dissipation by means of dynamic restitution coefficient for wet particles in liquid-solid fluidized beds is evaluated. The dynamic restitution coefficient model is based on a semi-empirical correlation generated from freely falling particles bouncing on a wet plate. We employed the Discrete Element Method (DEM) to numerically investigate the hydrodynamics of wet particles under the effect of interstitial fluid by incorporating dynamic restitution coefficient into damping coefficient. Simulation of the liquid-solid two-phase flow used a coupled DEM-Navier Stokes solver. Simulated distribution of granular pressure as well as particle velocities in the liquid fluidized beds were in good agreement with experimental data, thus the effects of dynamic restitution coefficient on the hydrodynamics of wet particle fluidization should be considered in numerical simulations. Two granular pressure models were also compared at different solid fraction for different particle sizes, the results indicated that Gidaspow's granular pressure model shows better predicted results when applied for small particles, while Batchelor's model provided more reasonable results for particles with larger diameter.