Effect of bed thickness on a pseudo 2D gas-solid fluidized bed turbulent flow structures and dynamics

Abstract

This work explores the ability of the two-fluid-model (TFM) to model the dynamical and turbulent features of a pseudo 2D gas-solid fluidized bed operated under slugging conditions. 2D and 3D numerical simulations are performed to investigate the effect of the bed thickness on predicted quantities. Hi fidelity raw pressure drop and particle velocity data from the NETL small scale challenge problem is processed and used to validate the CFD model. Our work shows that the differences between 2D and 3D simulations in predicting the fluidized bed dynamics using pressure fluctuation data is minimal. However the effect of the bed thickness on turbulent properties namely the normal Reynolds stresses, turbulent kinetic energy, granular temperatures is significant. Taking into account the bed thickness does not necessarily improve the model predictions of all the dynamic and turbulent features. Furthermore mean profiles alone are not sufficient to validate TFM models as is quite common in the open literature. Mixing in the slugging bed is predominantly due to coherent meso-scale structures (voids and slugs) rather than individual particles as revealed from computed granular temperatures.