Continuum description of particle-fluid flows is of fundamental importance. In the past, various averaging methods were developed to derive local quantities directly from particle scale information. However, it is not clear if the long-sought resolution-independence of the local quantities exists. Here, using a discrete element method, a statistical analysis is conducted for a gas-solid fluidized bed of monodispersed coarse particles under various conditions. The mean free path and time are first examined with the variation of inlet gas velocity. Then, the particle motion is analyzed according to the Langevin equation and it is revealed that the motion of individual particles in the driven system follows the fluctuation-dissipation relation. Finally, the particle collisional frequency and velocity distribution are analyzed. These distributions can achieve a steady state. The particle collisional frequency distribution deviates from the Gaussian distribution noticeably at high gas velocities. These findings lead to a better understanding of particle motion in a gas-solid fluidized bed and support the seeking of resolution-independent local quantities with averaging methods.
- Fluctuation-dissipation relation
- Fluidized beds
- Statistical analysis
- Steady state