Evaluation of bi-velocity methods in two-fluid model for granular flows : application to fluidized beds

Abstract

Rapid Granular Flows occur in a number of natural and industrial processes therefore the need to accurately describe these flows is apparent. The Euler-Euler based model of Kinetic Theory of Granular Flows is used to model fluidized bed systems within this thesis. Kinetic Theory of Granular Flows is still flawed in its development due to assumptions and simplifications required. This model needs further development to capture other various flow effects. This thesis will further develop the Kinetic Theory of Granular Flows by adding a correction of the Navier-Stokes equations and including nonNewtonian flow characteristics. It has been noted recently that the Navier-Stokes-Fourier equations do not describe compressible flows accurately. This has been attributed to the definition of fluid velocity in the derivation of fluid flow equations. In the incompressible flow regime, the derivation of the fluid flow is based on the velocity of the mass of the fluid. When fluids become compressed the mass flux will not change but the volume flux does change and gives an additional Volume velocity which affects the viscosity of the fluid. Korteweg Stress model provides another route to capture non-Newtonian phenomenon. These corrections to the Navier-Stokes system are extended and investigated into some Rapid Granular-Gas Flow equations in this thesis. The modifications to the Kinetic Theory of Granular Flows of the compressible volume velocity and the Korteweg approach are considered and tested on simple systems of a fluidized cylinder bed and a recirculating fluidized bed. A six-cyclone recirculating fluidized bed is then used as a larger and more complex system. It been found that by combining both modifications the overall results were improved.