Abstract: A three-dimensional random structure model of pellet packed bed for porous media is built based on the discrete element software of LIGGGHTS. The effectiveness of the random model has been verified by the calculation of the macroscopic flow resistance coefficient and the local porosity. A comparative study on the turbulence characteristics and vortex distribution within the porous structure has been carried out employing large eddy simulation (LES) and the conventional k-ε turbulence model. Simulation results show that the random structure model could predict the local porosity and the macroscopic resistance coefficient of the porous medium effectively. For the complex turbulent flow inside the porous structure, LES could give detailed information of the small vortices with diameter of 0.4-2.0mm within the porous structure and demonstrate the complex vortex structure in large pores of the porous medium. Besides, LES could also record the generation and development of the small vortex, and the process of stretching, splitting and disappearing of the large vortex within the local pores in detail, and the results are more consistent with the reality and the basic theory of turbulence. The LES study on turbulence characteristics in the random pellet packed bed in this paper will lay the foundation for the future simulation of filtration combustion.

Key words: porous media, pellet packed bed, random structure model, large eddy simulation, turbulence flow