Unified stability condition for particulate and aggregative fluidization-Exploring energy dissipation with direct numerical simulation

Fully resolved simulations of particulate and aggregative fluidization systems are performed successfully with the so-called combined lattice Boltzmann method and time-driven hard-sphere model (LBM-TDHS). In this method, the discrete particle phase is described by time-driven hard-sphere model, and the governing equations of the continuous fluid phase are solved with lattice Boltzmann method. Particle-fluid coupling is implemented by immersed moving boundary method. Time averaged flow structure of the simulated results show the formation of core-annulus structure and sigmoid distribution of voidage in the axial direction, which are typical phenomena in fluidization systems. Combining the results of the simulation, the energy consumption N-st for suspending and transporting solids is calculated from the direct numerical simulation (DNS) of fluidization, and the stability criterion N-st/N-T = min proposed in EMMS/bubbling model is verified numerically. Furthermore the numerical results show that the value of N-st/N-T in particulate fluidization is much higher than that in aggregative fluidization, but N-st/N-T = min is effective for both particulate and aggregative fluidization. (C) 2012 Chinese Society of Particuology and Institute of Process Engineering, Chinese Academy of Sciences. Published by Elsevier B.V. All rights reserved