Numerical simulation of particulate flow by the Eulerian-Lagrangian and the Eulerian-Eulerian approach with application to a fluidized bed

This work presents a computational study of the flow behavior of a lab-scale fluidized bed. The results obtained from a 'discrete particle method' (DPM) are qualitatively compared to the results obtained from a multi-fluid computational fluid dynamic (CFD) model. In the DEM, also referred as Eulerian-Lagrangian (EL) model, the two-dimensional motion of each individual spherical particle is directed calculated from the forces acting on them, accounting for the interaction between the particle and the gas-phase. The implemented collision model is based on the conservation laws for linear and angular momentum and requires, apart from geometrical factors, two empirical parameters: a restitution coefficient and a friction coefficient. The fluidynamic model of the gas is based on the volume-averaged Navier-Stokes equations. In the multi-fluid CFD model, also referred as Eulerian-Eulerian (EE), the gas and the solid phases are considered to be continuous and fully inter-penetrating. Both phases are described in terms of separate sets of conservation equations with appropriate interaction terms representing the coupling between the phases. Experiments results of a two-dimensional lab-scale bubbling fluidized bed are furthermore compared to the computational results obtained by the two approaches. A discussion about the obtained results and their discrepancies is presented.