Subgrid scale gas-particle stress model-based simulation of dense particle flows in a bubbling fluidized bed

Abstract

A novelty gas-particle stress model at subgrid scale level is proposed to consider the effect of gas turbulence on particle motions. The anisotropic characteristics of interaction between gas and particles are described by using a second-order moment model, the modeling of particle–particle collision is based on the kinetic theory of granular flow and the four-way coupling strategy is combined. A large eddy simulation is established to predict particles and bubble movements in a small-scale fluidized bed, simulation results are well agreed with the experimental data and the proposed model is validated. Results show that bubblelike granular temperature is greater than smaller-scale particle granular temperature and the flow patterns of two-phase turbulence are heterogeneously. Bubble motions have a great effect on particle dynamics. The distributions of axial and horizontal velocities of particles at center, middle and wall regions are approaching the normal distributions. The largest dominant frequency of particle concentration is 34.2 Hz at central region of lower bed height, approximately 1.3 times larger than that of wall region. Maximum ratios of wall to those central values are 8.3 for axial particle velocities.