Calibrating the Frictional-Pressure Model from Two-Fluid Simulation of Fluidised Beds in the Defluidisation Regime

The two-fluid simulation of a fluidised bed of non-adhesive particles, in which particles are represented as a continuous medium, requires a model for the pressure associated with particle contacts. While closures may be derived in the framework of the kinetic theory of granular flow for short-duration contacts, the frictional pressure associated with enduring particle contacts is generally modelled with an empirical closure involving several free parameters. This article proposes to use the experimental transition between the fluidised-bed and fixed-bed regimes in the determination of these parameters. The prediction of the minimum fluidisation velocity is shown to be governed by the frictional parameters, with either a discrete-element method or a two-fluid model. The shape of the particles, proxied by a sphericity coefficient, also influences the minimum fluidisation velocity. Such dependences of the model prediction can be used to select relevant frictional parameters, by comparison with experimental data or CFD-DEM simulation results.