Simulating the flow behavior of bubbles and particles in the bubbling fluidized bed by the method of direct simulation Monte Carlo and large eddy simulation

For the fluidized bed, based on the dense gas molecular dynamics and the gas-solid two-phase fluid hydro-dynamics of dense gas-solid flow, a discrete particle motion-collision decoupled model was developed. Particle collision was simulated by means of the direct simulation Monte Carlo (DSMC) approach. The large eddy simulation (LES) accounting on the effect of particle fluctuation was used to simulate the gas turbulent flow. The Newtonian equations of motion were solved for each individual particle in the system. The interaction between the gas phase and particles was taken into account by the Newtonian third law. Numerical simulations of the motion of bubbles and particles in a bubbling fluidized bed were performed and the distributions of particle concentration and probability density of axial and lateral velocities were obtained. Simulation results show that bubbles induce the circulation of particles in the fluidized bed in which the distribution of particle velocities can be expressed by the Gauss distribution. With the increase of particle concentration the particle temperature increases and reaches a maximum, then decreases. The domain frequency of instantaneous concentration of particle is in the range of 0.4-1.0 Hz, which agrees with the simulation result reported by Pain et.al (2001).