(172h) Quantitative Predictions of Instabilities in Solid-Particle Flows

The presence of clustering instabilities in gas-solid fluidized beds has been well documented experimentally and known to be a critical aspect of unit operation.  Predictions of such clusters via kinetic-theory models was first reported about two decades ago, with a plethora of studies since then demonstrating the qualitative ability of such models.  The quantitative ability of such models, however, has received relatively little attention.  In this work, we describe a series of studies designed to critically probe the accuracy of kinetic-theory models to predict instabilities in solid-particle flows.  The full, nonlinear solution of the transient form of the governing equations is solved.  A linear stability analysis of the same starting equations is also considered.  Predictions of the critical length scales obtained from both of these methods are compared with molecular dynamics simulations.  The results reveal the impact of friction, nonlinearities, and Knudsen effects on the formation and evolution of instabilities.  Overall, the quantitative performance of kinetic-theory models at predicting instabilities is quite encouraging.