Calculation of Granular Pressure By CFD-DEM Approach and Application to Stability Analysis in Solid-Liquid Fluidized Beds

As a critical concept in the kinetic theory of granular flow, the granular pressure is of great importance to understand and model many other phenomena in the fluidization process such as stability, heat transfer, erosion, attrition, etc. This paper presents a method based on the Computational Fluid Dynamics-Discrete Element Method (CFD-DEM) coupling approach to calculate the collisional part of the particle pressure in a solid-liquid fluidized bed without resorting to any empirical assumptions or use of formulas from the kinetic theory of granular flow. The collisional particle pressure was directly calculated as the forces acting on the containing walls by the particles. The simulation was set up as and validated qualitatively against the experimental measurements of Zenit et al. (1997). The sensitivity analysis of the approach to the model parameters showed that the calculated granular pressure was insensitive to the material properties of the particles. It was also found that the calculated particle pressure was a function of solid volume fraction; and a maximum particle pressure appeared at the intermediate solid concentration. The peak value appeared to be associated with the transition condition of the fluidized bed. Consequently, the peak value as an indicator of the stability condition was examined by performing another set of simulations based on the work of Ghatage et al. (2014). It was found that the CFD-DEM simulation transition regime based on the granular pressure was in good agreement with both the experiment observations as well as that from one-dimensional linear stability analysis.